CN109627995B

CN109627995B - Pressure-sensitive adhesive sheet with release film

Info

Publication number: CN109627995B
Application number: CN201811157672.8A
Authority: CN
Inventors: 定司健太; 樋口真觉; 加藤直宏; 武蔵岛康
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2017-10-06
Filing date: 2018-09-30
Publication date: 2022-09-23
Anticipated expiration: 2038-09-30
Also published as: KR20190039865A; JP2019070072A; JP7240806B2; EP3521395A1; CN109627995A; US20190106606A1

Abstract

[ problem ] to]The invention provides an adhesive sheet with a peeling film, which is not easy to generate unintended separation phenomenon. [ solution ]]Provided is a release film-equipped adhesive sheet which comprises: the adhesive sheet includes a double-sided adhesive sheet, a first release film disposed on a first adhesive surface of the adhesive sheet, and a second release film disposed on a second adhesive surface of the adhesive sheet. In the pressure-sensitive adhesive sheet with a release film, the tensile modulus E of the second release film ₂ Tensile modulus E relative to the first release film ₁ Ratio of (E) ₂ /E ₁ ) Is 1.5 or more.

Description

Pressure-sensitive adhesive sheet with release film

Technical Field

The present invention relates to a pressure-sensitive adhesive sheet with a release film.

Background

In general, an adhesive (also referred to as a pressure-sensitive adhesive hereinafter) is in a soft solid (viscoelastic material) state in a temperature range around room temperature, and has a property of being easily adhered to an adherend by pressure. By utilizing such properties, adhesives are widely used in various industrial fields such as home electric appliances, automobiles, OA equipment, and the like, for example, in the form of a substrate-attached adhesive sheet having an adhesive layer on a supporting substrate, or in the form of a substrate-free adhesive sheet having no supporting substrate. In recent years, adhesive sheets used for the purpose of bonding, fixing, protecting, etc. members in smart phones and other portable devices have been gaining importance. Patent documents 1 to 4 are cited as technical documents relating to a double-sided adhesive tape used for fixing members of a portable electronic device.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-132911

Patent document 2: japanese patent laid-open publication No. 2013-100485

Patent document 3: japanese patent laid-open publication No. 2017-002292

Patent document 4: japanese patent laid-open publication No. 2015-147873

Disclosure of Invention

Problems to be solved by the invention

The fixation of members in portable electronic devices based on adhesive sheets is generally small in adhesive area due to limitations in size, weight, and the like. The pressure-sensitive adhesive sheet used for this application must have an adhesive strength capable of achieving good fixation even in a small area, and the required performance thereof is changing from the demand for weight reduction and size reduction to the demand for higher levels. In order to improve productivity of products such as electronic devices and reduce production costs, it is first studied to reduce takt time (process operation time). The pressure-sensitive adhesive sheet to be used is required to have a simple adhesiveness by light pressure bonding and to exhibit desired performance in a shorter aging time. Therefore, it is necessary to exhibit good adhesion force from immediately after the attachment.

From the viewpoint of exhibiting good performance even in a small area and from the viewpoint of reducing the tact time of application, it is advantageous to make the pressure-sensitive adhesive surface (surface of the pressure-sensitive adhesive layer) of the pressure-sensitive adhesive sheet highly smooth. This is because, if the smoothness of the pressure-sensitive adhesive surface is high, a good adhesion state between the pressure-sensitive adhesive surface and the surface of the adherend can be quickly achieved, and the initial adhesiveness tends to be improved. Since the surface shape of the pressure-sensitive adhesive surface can reflect the surface shape of a release liner for protecting the pressure-sensitive adhesive surface in the pressure-sensitive adhesive sheet before use, a release liner having high smoothness is also preferably used as the release liner. A release liner made of a resin film as a base material (hereinafter, also referred to as a release film) generally has higher surface smoothness and is suitable for high smoothing of a pressure-sensitive adhesive surface than a release liner made of paper as a base material.

However, in a release film-equipped pressure-sensitive adhesive sheet in which both sides of the pressure-sensitive adhesive sheet having double-sided adhesiveness are protected by release films, when the release film covering one surface of the pressure-sensitive adhesive sheet is removed from the one surface, the following phenomenon is likely to occur: the phenomenon of so-called "unintended separation" in which the other surface of the pressure-sensitive adhesive sheet is lifted up from the release film covering the other surface, and further, a part of the pressure-sensitive adhesive sheet is broken from the remaining pressure-sensitive adhesive sheet and removed together with the release film on the one surface. This unintended separation phenomenon is a factor of reducing handling properties of the pressure-sensitive adhesive sheet, reducing workability, and reducing yield. In order to prevent the unintended separation phenomenon, it is effective that: the releasability of the release film on the other surface is sufficiently lower (the release force is increased) than the releasability of the release film on the one surface. However, if the releasability of the release film on the other surface is reduced (re-peeling is performed), the transferability when the pressure-sensitive adhesive sheet on the release film on the other surface is transferred to an adherend after the release film on the one surface is removed tends to be reduced. In addition, the pressure-sensitive adhesive sheet is sometimes used in a form in which the pressure-sensitive adhesive sheet is transferred to another release liner (hereinafter, also referred to as a process liner) in order to further process the pressure-sensitive adhesive sheet before it is attached to a final adherend, for example. That is, the adherend of the pressure-sensitive adhesive sheet may be a releasable adherend such as the process liner described above. In this case, in order to transfer the pressure-sensitive adhesive sheet on the release film on the other surface to a releasable adherend, the releasability of the releasable adherend must be lower than that of the release film on the other surface. It becomes more difficult to transfer the pressure-sensitive adhesive sheet on such a releasable adherend to a final adherend or a subsequent process liner.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a pressure-sensitive adhesive sheet with a release film, which is less likely to cause unintended separation.

Means for solving the problems

According to the present specification, there is provided a release film-equipped adhesive sheet comprising: the pressure-sensitive adhesive sheet includes a double-sided pressure-sensitive adhesive sheet, a first release film disposed on a first pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet, and a second release film disposed on a second pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet. Tensile modulus E of the second release film ₂ Tensile modulus E relative to the first release film ₁ Ratio of (E) ₂ /E ₁ ) Is 1.5 or more. By using the first release film having such lower rigidity than the second release filmThe film tends to suppress the occurrence of an unintended separation phenomenon when the first release film is removed from the first adhesive surface. This prevents unintended separation and further reduces the difference in peeling force between the second release film and the first release film. As a result, the second release film having higher releasability can be used, and the transferability of the pressure-sensitive adhesive sheet from the second release film to an adherend or a process liner can be improved.

With respect to the release film-attached adhesive sheet of some embodiments, the peeling force R from the above-mentioned second release film is ₂ Subtracting the peeling force R of the first peeling film ₁ And the difference in peel force (R) defined in the form of the value obtained ₂ -R ₁ ) It may be 0.2N/50mm or less. According to the technology disclosed in the present specification, even if the difference in peeling force is made so small, the unintended separation phenomenon can be appropriately suppressed.

The maximum test force of the first release film in a tensile test is preferably 5N or more. Such a first release film is advantageous from the viewpoint of handling properties and dimensional stability of the first release film.

The maximum test force of the second release film in the tensile test is preferably 30N or more. A release film-equipped pressure-sensitive adhesive sheet having such a second release film is advantageous from the viewpoint of workability in removing the first release film.

In some embodiments, a release polyolefin film may be preferably used as the first release film. By using a releasable polyolefin film as the first release film, it is possible to suitably realize the film satisfying the above-mentioned ratio (E) ₂ /E ₁ ) The pressure-sensitive adhesive sheet with a release film of (1).

In some embodiments, as the second release film, a releasable polyester film can be preferably used. By using a releasable polyester film as the second release film, it is possible to suitably realize the effect of satisfying the above-mentioned ratio (E) ₂ /E ₁ ) The pressure-sensitive adhesive sheet with a release film of (1).

In some embodiments, the adhesive layer constituting the adhesive sheet may have a storage modulus G' at 25 ℃ of 0.6MPa or less. It is particularly significant to apply the technology disclosed in the present specification to a pressure-sensitive adhesive sheet with a release film having such a pressure-sensitive adhesive layer to prevent unintended separation.

In some embodiments, the adhesive sheet is a substrate-free adhesive sheet formed of an adhesive layer. The pressure-sensitive adhesive sheet having such a structure is generally easy to deform and therefore easily adheres to the surface of an adherend, and tends to be easily separated unintentionally as compared with a pressure-sensitive adhesive sheet with a substrate. Therefore, it is of great interest to apply the techniques disclosed herein to inhibit unintended separations.

Drawings

Fig. 1 is a schematic sectional view showing a release film-attached adhesive sheet according to an embodiment.

Fig. 2 is a schematic sectional view showing another embodiment of an adhesive sheet with a release film.

Description of the reference numerals

1.3 pressure-sensitive adhesive sheet

1A, 3A first side (first adhesive side)

1B, 3B second side (second adhesive side)

11 adhesive layer

11A one surface

11B another surface

21 first Release film

21A surface (first stripping surface)

21B back surface

22 second Release film

22A surface (second stripping surface)

31 first adhesive layer

32 second adhesive layer

35 supporting the substrate

100. 300 pressure-sensitive adhesive sheet with release film

Detailed Description

Suitable embodiments of the present invention are described below. It is to be noted that matters necessary for carrying out the present invention other than the matters specifically mentioned in the present specification can be understood by those skilled in the art based on the teaching of the practice of the invention described in the present specification and the common general knowledge at the time of application. The present invention can be implemented based on the contents disclosed in the present specification and the common general knowledge in the art. In the following drawings, members and portions that exhibit the same function are sometimes described with the same reference numerals, and redundant description may be omitted or simplified. The embodiments shown in the drawings are schematic for the purpose of clearly illustrating the present invention, and do not necessarily show the size or scale of the psa sheet of the present invention actually provided as a product.

In the present specification, the "pressure-sensitive adhesive" refers to a material that exhibits a soft solid (viscoelastic material) state in a temperature range around room temperature and has a property of easily adhering to an adherend by pressure as described above. As used herein, an adhesive such as "c.a. dahlquist," bonding: basis and Practice ("Adhesion: Fundamentals and Practice"), McLaren&Sons, (1966) P.143 ", generally speaking, can be a compound having a complex tensile modulus E (1Hz)<10 ⁷ dyne/cm ² A material having the above properties (typically, a material having the above properties at 25 ℃).

In this specification, "(meth) acryloyl" is used inclusively to mean both acryloyl and methacryloyl. Likewise, "(meth) acrylate" inclusively refers to the meaning of acrylate and methacrylate, and "(meth) acrylic acid" inclusively refers to acrylic acid and methacrylic acid.

In this specification, the "acrylic polymer" refers to a polymer containing, as a monomer unit constituting the polymer, a monomer unit derived from a monomer having at least 1 (meth) acryloyl group in 1 molecule. Hereinafter, a monomer having at least 1 (meth) acryloyl group in 1 molecule is also referred to as an "acrylic monomer". The acrylic polymer in this specification is defined as a polymer comprising monomer units derived from an acrylic monomer.

< pressure-sensitive adhesive sheet with Release film >

The release film-equipped adhesive sheet disclosed herein is configured to include a sheet-shaped (strip-shaped) adhesive sheet having a first adhesive surface and a second adhesive surface, a first release film disposed on the first adhesive surface of the adhesive sheet, and a second release film disposed on the second adhesive surface of the adhesive sheet.

Fig. 1 shows a structure of a release film-attached pressure-sensitive adhesive sheet according to an embodiment. The pressure-sensitive adhesive sheet with a release film 100 includes a substrate-free pressure-sensitive adhesive sheet 1 formed of a pressure-sensitive adhesive layer 11. One surface of the adhesive sheet 1 is a first adhesive surface 1A formed by one surface 11A of the adhesive layer 11, and the other surface of the adhesive sheet 1 is a second adhesive surface 1B formed by the other surface 11B of the adhesive layer 11. The pressure-sensitive adhesive layer 11 may have a single-layer structure or a multilayer structure having 2 or more layers. The adhesive layers constituting the multilayer structure may be the same or different in composition (material, thickness, etc.). From the viewpoint of productivity and performance stability, a mode in which the adhesive layer 11 has a single-layer structure can be preferably employed.

Here, the substrate-less double-sided adhesive sheet refers to a double-sided adhesive sheet that does not include a non-releasable support substrate between the first adhesive surface and the second adhesive surface. The non-releasable support substrate refers to a support substrate that is not intended to be separated from the adhesive layer during use of the adhesive sheet including the support substrate.

The first pressure-sensitive adhesive surface 1A of the pressure-sensitive adhesive sheet 1 is protected by a first release film 21 disposed on the first pressure-sensitive adhesive surface 1A. The second pressure-sensitive adhesive surface 1B of the pressure-sensitive adhesive sheet 1 is protected by a second release film 22 disposed on the second pressure-sensitive adhesive surface 1B. The tensile modulus E of the first release film 21 and the second release film 22 is defined by the tensile modulus E of the second release film 22 ₂ Tensile modulus E relative to first release film 21 ₁ Ratio of (E) ₂ /E ₁ ) Is selected so as to be 1.5 or more.

Both the surface (first release surface) 21A of the first release film 21 in contact with the first pressure-sensitive adhesive surface 11A and the surface (second release surface) 22A of the second release film 22 in contact with the second pressure-sensitive adhesive surface 11B become release surfaces, i.e., surfaces from which the pressure-sensitive adhesive layer can be released. Peeling force R of the first peeling surface 21A ₁ And the peeling force R of the second peeling surface 22A ₂ By difference in peel force (R) ₂ -R ₁ ) Set to 0.2N/50mm or less. The first release film 21 is opposite to the first release surface 21AThe side surface 21B may be a release surface or a non-release surface. Similarly, the surface 22B of the second release film 22 opposite to the second release surface 22A may be a release surface or a non-release surface.

The release film-attached pressure-sensitive adhesive sheet 100 thus configured can be suitably used in the following manner: first, the first release film 21 is peeled off from the first pressure-sensitive adhesive surface 1A to pressure bond the thus exposed first pressure-sensitive adhesive surface 1A to the first adherend, and thereafter, the second release film 22 is peeled off from the second pressure-sensitive adhesive surface 1B to pressure bond the thus exposed second pressure-sensitive adhesive surface 1B to the second adherend. The adherend may be an adherend to which the pressure-sensitive adhesive sheet 1 is finally attached, or may be a release surface of a process liner. The process liner can be used for the purpose of subjecting the pressure-sensitive adhesive sheet 1 to various processes or treatments before the pressure-sensitive adhesive sheet 1 is finally attached to an adherend, for the purpose of transporting the pressure-sensitive adhesive sheet 1, or the like. Examples of the processing or treatment include processing for fitting the outer shape of the pressure-sensitive adhesive sheet to the shape of the final adherend by punching, cutting, or the like, and processing for preparing the pressure-sensitive adhesive sheet into a form suitable for enhancing the efficiency and accuracy of the attaching operation to the adherend.

Fig. 2 shows a structure of a release film-equipped pressure-sensitive adhesive sheet according to another embodiment. The pressure-sensitive adhesive sheet with release film 300 comprises a pressure-sensitive adhesive sheet with substrate 3, and the pressure-sensitive adhesive sheet with substrate 3 comprises a non-releasable support substrate 35, a first pressure-sensitive adhesive layer 31 covering one surface of the support substrate 35, and a second pressure-sensitive adhesive layer 32 covering the other surface of the support substrate 35. One surface of the adhesive sheet 3 is a first adhesive surface 3A formed by one surface of the first adhesive layer 31, and the other surface of the adhesive sheet 3 is a second adhesive surface 3B formed by one surface of the second adhesive layer 32. The first pressure-sensitive adhesive layer 31 and the second pressure-sensitive adhesive layer 32 may each independently have a single-layer structure, or may have a multilayer structure of 2 or more layers. The adhesive layers constituting the multilayer structure may be the same or different in composition (material, thickness, etc.). From the viewpoint of productivity and performance stability, a mode in which both the first pressure-sensitive adhesive layer 31 and the second pressure-sensitive adhesive layer 32 have a single-layer structure can be preferably employed.

The first pressure-sensitive adhesive surface 3A of the pressure-sensitive adhesive sheet 3 is protected by a first release film 21 disposed on the first pressure-sensitive adhesive surface 3A. The second pressure-sensitive adhesive surface 3B of the pressure-sensitive adhesive sheet 3 is protected by a second release film 22 disposed on the second pressure-sensitive adhesive surface 3B. As the first release film 21 and the second release film 22 constituting the release film-equipped adhesive sheet 300, the same release films as the first release film 21 and the second release film 22 of the release film-equipped adhesive sheet 100 shown in fig. 1 can be used. The release film-attached pressure-sensitive adhesive sheet 300 configured in this way can be suitably used in the following manner, as in the release film-attached pressure-sensitive adhesive sheet 100: first, the first release film 21 is peeled off from the first pressure-sensitive adhesive surface 3A to pressure bond the thus exposed first pressure-sensitive adhesive surface 3A to the first adherend, and thereafter, the second release film 22 is peeled off from the second pressure-sensitive adhesive surface 3B to pressure bond the thus exposed second pressure-sensitive adhesive surface 3B to the second adherend.

< Release film >

The first release film and the second release film may be selected from various release liners having a resin film as a base (release film base) in such a manner that unintended separation is suppressed. From the viewpoint of surface smoothness, a resin film having a non-porous structure and typically containing substantially no air bubbles (having no voids) can be preferably used as the release film substrate. The resin film may have a single-layer structure or a multilayer structure (for example, a three-layer structure) having two or more layers.

Examples of the resin material constituting the release film base material include a fluororesin such as a polyester resin, a polyolefin resin, a polyamide resin (PA), a polyimide resin (PI), a polyamideimide resin (PAI), a polyether ether ketone resin (PEEK), a polyether sulfone resin (PES), a polyphenylene sulfide resin (PPS), a polycarbonate resin (PC), a polyurethane resin (PU), an ethylene-vinyl acetate resin (EVA), or Polytetrafluoroethylene (PTFE), and an acrylic resin. Here, the polyester resin means a resin containing a polyester at a ratio exceeding 50% by weight. Similarly, the polyolefin resin means a resin containing polyolefin at a ratio exceeding 50% by weight. The same applies to other resins.

The release film substrate may be formed using a resin material containing 1 kind of such resin alone, or may be formed using a resin material containing 2 or more kinds of such resins mixed therein. The resin film may be unstretched or stretched (uniaxially stretched or biaxially stretched).

As the polyester resin, typically, a polyester resin containing as a main component a polyester obtained by polycondensing a dicarboxylic acid and a diol can be used.

Examples of the dicarboxylic acid constituting the polyester include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, 2-methyl terephthalic acid, 5-sulfoisophthalic acid, 4 ' -diphenyl dicarboxylic acid, 4 ' -diphenyl ether dicarboxylic acid, 4 ' -diphenyl ketone dicarboxylic acid, 4 ' -diphenoxyethanedicarboxylic acid, 4 ' -diphenyl sulfone dicarboxylic acid, 1, 4-naphthalenedicarboxylic acid, 1, 5-naphthalenedicarboxylic acid, 2, 6-naphthalenedicarboxylic acid, and 2, 7-naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as 1, 2-cyclohexanedicarboxylic acid, 1, 3-cyclohexanedicarboxylic acid, and 1, 4-cyclohexanedicarboxylic acid; aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, and fumaric acid; derivatives thereof (e.g., lower alkyl esters of the above dicarboxylic acids such as terephthalic acid); and the like. These can be used alone in 1 or a combination of 2 or more. As the polyester resin used in the second release film, the suitable elastic modulus ratio (E) disclosed herein can be easily realized from the relationship with the first release film ₂ /E ₁ ) From the viewpoint of the like, aromatic dicarboxylic acids are preferred. Among them, preferable dicarboxylic acids include terephthalic acid and 2, 6-naphthalenedicarboxylic acid. For example, 50% by weight or more (for example, 80% by weight or more, typically 95% by weight or more) of the dicarboxylic acids constituting the polyester are preferably terephthalic acid, 2, 6-naphthalenedicarboxylic acid, or a combination thereof. The dicarboxylic acid may be substantially composed of only terephthalic acid, substantially composed of only 2, 6-naphthalenedicarboxylic acid, or substantially composed of only terephthalic acid and 2, 6-naphthalenedicarboxylic acid.

Examples of the diol constituting the polyester include aliphatic diols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1, 3-propanediol, 1, 5-pentanediol, neopentyl glycol, 1, 4-butanediol, 1, 6-hexanediol, 1, 8-octanediol, and polyoxytetramethylene glycol; alicyclic diols such as 1, 2-cyclohexanediol, 1, 4-cyclohexanediol, 1-dimethylolcyclohexane and 1, 4-dimethylolcyclohexane, aromatic diols such as benzenedimethanol, 4 '-dihydroxybiphenyl, 2-bis (4' -hydroxyphenyl) propane and bis (4-hydroxyphenyl) sulfone; and the like. These can be used alone in 1 or a combination of 2 or more. From the viewpoint of transparency and the like, aliphatic diols are preferred, and ethylene glycol is particularly preferred. The proportion of the aliphatic diol (preferably ethylene glycol) in the diol constituting the polyester is preferably 50% by weight or more (for example, 80% by weight or more, typically 95% by weight or more). The diol may be substantially composed of only ethylene glycol.

Examples of the polyester resin film include a polyethylene terephthalate (PET) film, a polybutylene terephthalate (PBT) film, a polyethylene naphthalate (PEN) film, and a polybutylene naphthalate film.

As the polyolefin resin, 1 kind of polyolefin may be used alone or 2 or more kinds of polyolefins may be used in combination. The polyolefin may be, for example, a homopolymer of an α -olefin, a copolymer of 2 or more α -olefins, a copolymer of 1 or 2 or more α -olefins with other vinyl monomers, or the like. Specific examples thereof include ethylene-propylene copolymers such as Polyethylene (PE), polypropylene (PP) and Ethylene Propylene Rubber (EPR), ethylene-propylene-butene copolymers, ethylene-butene copolymers and ethylene-ethyl acrylate copolymers. Any of Low Density (LD) polyolefins and High Density (HD) polyolefins may be used. Examples of the polyolefin resin film include a non-oriented polypropylene (CPP) film, a biaxially oriented polypropylene (OPP) film, a Low Density Polyethylene (LDPE) film, a Linear Low Density Polyethylene (LLDPE) film, a Medium Density Polyethylene (MDPE) film, a High Density Polyethylene (HDPE) film, a Polyethylene (PE) film in which 2 or more kinds of Polyethylenes (PE) are mixed, and a PP/PE mixed film in which polypropylene (PP) and Polyethylene (PE) are mixed.

As the first release film, for example, a release polyolefin resin film can be preferably used. In this specification, the releasable resin film means a resin film having a releasable surface on at least the pressure-sensitive adhesive layer side. As the polyolefin resin film, polyethylene resin films such as LDPE film, LLDPE film, and LDPE/LLDPE blend film; polypropylene resin films such as a CPP film and an OPP film; PP/PE mixed film; and the like, but are not limited thereto. In some embodiments, a release polyolefin resin film having a release treatment layer on at least the pressure-sensitive adhesive layer-side surface of a polyethylene resin film such as an LDPE film, an LLDPE film, or an LDPE/LLDPE blend film can be preferably used as the first release film.

As the second release film, for example, a releasable polyester resin film can be preferably used. As the polyester resin film, a PET film, a PBT film, a PEN film, or the like can be used, but the polyester resin film is not limited thereto. In some embodiments, a release polyester resin film having a release treatment layer on at least the pressure-sensitive adhesive layer-side surface of a PET film or a PBT film may be preferably used as the second release film. Alternatively, a releasable polyolefin resin film may be used as the second release film. For example, a release polyolefin resin film having a release treatment layer on at least the pressure-sensitive adhesive layer-side surface of a polypropylene resin film such as a CPP film or an OPP film can be used as the second release film.

Examples of the combination of the first release film and the second release film include, but are not particularly limited to, a combination of a releasable polyethylene resin film (e.g., a releasable LDPE film) as the first release film and a releasable polyester resin film (e.g., a releasable PET film) as the second release film; a combination of a releasable polyethylene resin film (e.g., a releasable LDPE film) as a first release film and a releasable polypropylene resin film (e.g., a releasable OPP film or a releasable CPP film) as a second release film; and the like.

The release film substrate may contain, as necessary, known additives such as a light stabilizer, an antioxidant, an antistatic agent, a colorant (dye, pigment, etc.), a filler, a slipping agent, and an antiblocking agent, within a range not significantly impairing the effects of the present invention. The amount of the additive to be blended is not particularly limited, and may be appropriately set according to the use mode of the psa sheet with a release film, etc.

In some embodiments, one or both of the first release film and the second release film may contain a colorant. By including a colorant in at least one of the release films, the visibility of the first release film and the second release film can be improved. For example, by using a transparent film as the second release film while the first release film contains a colorant, it is possible to quickly and easily determine which of the first release films is the first release film. This can shorten the tact time and prevent an operation error to improve the yield.

The colorant is not particularly limited, and conventionally known pigments and dyes can be used. Non-limiting examples of the pigment include inorganic pigments such as titanium oxide (titanium dioxide such as rutile type titanium dioxide and anatase type titanium dioxide), zinc oxide, calcium carbonate (light calcium carbonate, heavy calcium carbonate, etc.), barium carbonate, magnesium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc carbonate, zinc sulfide, talc, kaolin, barium sulfate, silica, alumina, zirconia, magnesium oxide, lithium fluoride, calcium fluoride, iron oxide, iron hydroxide, chromium oxide, spinel type calcined type, chromic acid type, molybdate orange type, deep blue type, aluminum powder type, bronze powder type, and calcium phosphate; organic pigments such as phthalocyanine-based, azo-based, condensed azo-based, azo lake (azo lake) -based, anthraquinone-based, perylene-violanthrone-based, indigo-thioindigo-based, isoindolinone-based, azomethine azo-based, dioxazine-based, quinacridone-based, aniline black-based, triphenylmethane-based, and carbon black-based; and so on.

Examples of the dye include azo dyes, anthraquinone dyes, quinophthalone dyes, styrene dyes, diphenylmethane dyes, triphenylmethane dyes, oxazine dyes, triazine dyes, xanthan dyes, methane dyes, azomethine dyes, acridine dyes, and diazine dyes.

The color of the colorant is not particularly limited, and may be, for example, white, gray, black, red, cyan, yellow, green, yellow-green, orange, violet, gold, silver, pearl, or the like. As a preferable example, white color can be given.

The method for producing the release film substrate is not particularly limited. For example, conventionally known common resin film forming methods such as extrusion molding, inflation molding, T-die casting molding, calender roll molding, and the like can be suitably used.

As the release film, a release film having a release treatment layer on at least one surface of such a release film substrate can be preferably used. The one surface is a surface on the side of the release film opposite to the pressure-sensitive adhesive layer (hereinafter, also referred to as a front surface). The release treatment layer may be provided on the other surface (hereinafter, also referred to as the back surface) of the release film base material, or may not be provided. The method for forming the release-treated layer is not particularly limited. For example, the release film base material may be subjected to a surface treatment with a known release treatment agent to form the release treatment layer. Examples of the release treatment agent include silicone release treatment agents, long-chain alkyl release treatment agents, fluorine release treatment agents, molybdenum (IV) sulfide, and the like. In some embodiments, a release film having a release treatment layer based on a silicone-based release treatment agent may be preferably used.

(tensile modulus)

In some embodiments of the release film-attached adhesive sheet disclosed herein, the first release film and the second release film may have a tensile modulus E of the second release film ₂ Tensile modulus E relative to the first release film ₁ Ratio of (E) ₂ /E ₁ ) Is selected so as to be 1.5 or more. Hereinafter, the above ratio (E) will also be described ₂ /E ₁ ) Referred to as "elastic modulus ratio (E) ₂ /E ₁ )”。

The tensile modulus of the release film can be calculated as follows: a measurement sample having an appropriate size was cut out from the release film to be measured, and the test piece was subjected to a tensile test in which the test piece was stretched in the above-mentioned one direction at room temperature (23 ℃) in accordance with JIS K7127, and the linear regression of the stress-strain curve obtained from the tensile test piece was calculated. More specifically, a measurement sample was prepared by cutting a release film to be measured into a strip shape having a width of 10mm, and the measurement sample was held between 20mm each at both ends by chucks of a universal tensile testing machine, and the tensile test was performed under conditions of an inter-chuck distance of 60mm and a tensile speed of 150 mm/min. The measurement sample is preferably produced such that the longitudinal direction (MD) of the release film coincides with the stretching direction of the sample. The tensile modulus of each release film used in examples described later was measured by the method described above.

According to the technique disclosed herein, by making the elastic modulus ratio (E) ₂ /E ₁ ) By selecting the first release film and the second release film so as to be 1.5 or more, the occurrence of unintended separation phenomenon can be effectively suppressed. Without wishing to be bound by theory, the reason for obtaining such an effect is considered as follows, for example. That is, when the first release film is peeled from the first adhesive surface, the first release film is generally peeled by being gradually curled in a direction away from the first adhesive surface from the peeling start end. At this time, the portion of the first release film which is to be separated from the first adhesive surface is pressed against the first adhesive surface due to the repulsive force of the curled first release film to return to its original shape. It is presumed that the pressing force locally improves the adhesion between the first release film and the first pressure-sensitive adhesive surface, which causes the pressure-sensitive adhesive sheet attached to the first release film to be easily lifted from the second release film, and further causes unintended separation to be easily caused. Since a release film having a high tensile modulus has high bending rigidity as a whole, the pressure-sensitive adhesive surface tends to be pressed more strongly by the repulsive force. By using the first release film having a lower tensile modulus than the second release film, the pressing force to the pressure-sensitive adhesive surface when the first release film is peeled can be reduced. Further, by using the second release film having a higher tensile modulus than the first release film, the second release film and the pressure-sensitive adhesive sheet held thereon have good shape stability, and the operation of peeling the first release film from the first pressure-sensitive adhesive surface can be smoothly performed. It is believed that this also helps to inhibit unintended detachment.

In some embodiments, the elastic modulus ratio (E) ₂ /E ₁ ) For example, it may be 1.7 or more, or 2.0 or more. Ratio of elastic modulus (E) ₂ /E ₁ ) When the size is larger, the separation preventing property tends to be improved undesirably. From this viewpoint, in some embodiments, the elastic modulus ratio (E) ₂ /E ₁ ) For example, the content may be 3.0 or more, 5.0 or more, 6.0 or more, or 8.0 or more. Modulus of elasticity ratio (E) ₂ /E ₁ ) The upper limit of (b) is not particularly limited. In some embodiments, the elastic modulus ratio (E) is selected from the group consisting of the ease of manufacturing the first and/or second release films and the handleability ₂ /E ₁ ) For example, the content may be 50 or less, 40 or less, 30 or less, 25 or less, 20 or less, or 15 or less. Modulus of elasticity ratio (E) ₂ /E ₁ ) Can be adjusted by the choice of the first and second release films.

Tensile modulus E of the first Release film ₁ There is no particular limitation. From the viewpoint of handling properties (e.g., dimensional stability, ease of processing, etc.) of the first release film itself, the tensile modulus E is generally ₁ It is preferably 0.05GPa or more, but may be 0.1GPa or more, or 0.15GPa or more. In some embodiments, tensile modulus E may also be used ₁ The first release film is 0.3GPa or more, for example 0.5GPa or more. In addition, an appropriate elastic modulus ratio (E) can be easily achieved ₂ /E ₁ ) From the viewpoint of tensile modulus E ₁ Usually, it is preferably 4.0GPa or less, more preferably 3.0GPa or less, further preferably 2.0GPa or less, further preferably 1.5GPa or less, further preferably 1.2GPa or less. In some embodiments, it may be preferred to employ tensile modulus E ₁ The first release film is 0.8GPa or less, 0.6GPa or less, or 0.4GPa or less. Tensile modulus E ₁ The material and the manufacturing method of the first release film can be adjusted.

Tensile modulus E of the second Release film ₂ There is no particular limitation. Tensile modulus E of the second Release film ₂ Usually, it is preferably 0.3GPa or more, and more preferably 0.5GPa or more. Easy compatibility between the handling property of the first release film and an appropriate elastic modulus ratio (E) ₂ /E ₁ ) From the viewpoint of (1), in some embodiments, stretchingModulus E ₂ For example, the amount of the carbon dioxide may be 0.7GPa or more, 0.9GPa or more, 1.3GPa or more, 1.5GPa or more, or 1.7GPa or more. In addition, from the viewpoint of handling properties (e.g., ease of winding) of the second release film, the tensile modulus E in some embodiments ₂ For example, it may be 10GPa or less, preferably 6.0GPa or less, 5.0GPa or less, 4.0GPa or less, or 3.0GPa or less. Tensile modulus E ₂ The material and the manufacturing method of the second release film can be adjusted.

In some embodiments, the first release film has a maximum test force F in a tensile test ₁ Preferably 5N or more. Such a first release film is advantageous from the viewpoint of handling properties and dimensional stability of the first release film. The above maximum test force F ₁ For example, the number of the holes may be 7N or more, 9N or more, 12N or more, or 15N or more. Maximum test force F ₁ The upper limit of (b) is not particularly limited. In some embodiments, the maximum test force F ₁ For example, 120N or less, 100N or less, 80N or less, 60N or less, 40N or less, or 25N or less may be used.

In some embodiments, the second release film has a maximum test force F in a tensile test ₂ Preferably 30N or more. Such a second release film is advantageous from the viewpoint of workability when leaving the adhesive sheet on the second release film and removing the first release film from the adhesive sheet, because of high shape retention. Maximum test force F ₂ It is also preferable from the viewpoint of handling property and dimensional stability of the pressure-sensitive adhesive sheet with a release film. Maximum test force F ₂ For example, the number of the holes may be 40N or more, 50N or more, or 65N or more. Maximum test force F ₂ The upper limit of (b) is not particularly limited. From the viewpoint of handling property (e.g., ease of winding) of the second release film, the maximum test force F in some embodiments ₂ For example, the number of the holes may be 500N or less, 300N or less, 200N or less, or 150N or less.

Maximum test force F ₁ 、F ₂ Can be grasped based on the results of the tensile test. Maximum test force F ₁ 、F ₂ For example, the material, production method, thickness, and the like of the first and second release films can be adjusted.

Maximum strain epsilon of first release film ₁ There is no particular limitation. In some embodiments, the maximum strain ε ₁ For example, the content may be 150% or more, 175% or more, or 200% or more. Maximum strain epsilon ₁ The large first release film tends to exhibit good flexibility. Therefore, the pressure-sensitive adhesive sheet with a release film disclosed herein can be preferably used as the first release film. Maximum strain ε from the viewpoint of handling properties of the first release film ₁ Usually, 1000% or less is suitable, and may be 700% or less, 500% or less, or 400% or less.

Maximum strain epsilon of second release film ₂ There is no particular limitation. In some embodiments, the maximum strain ε ₂ For example, it may be 300% or less, 250% or less, or 200% or less. Maximum strain epsilon ₂ The small second release film has high shape retention, and the operation of leaving the adhesive sheet on the second release film and removing the first release film is easy. Therefore, the pressure-sensitive adhesive sheet can be preferably used as the second release film of the release film-attached pressure-sensitive adhesive sheet disclosed herein. Maximum strain epsilon ₂ The lower limit of (b) is not particularly limited, but is usually 70% or more, preferably 100% or more, and also preferably 120% or more, from the viewpoint of handleability of the second release film. In some embodiments, the maximum strain ε may be used ₂ 150% or more or 180% or more of the second release film.

Maximum strain epsilon ₁ 、ε ₂ Can be grasped based on the results of the tensile test. Maximum strain epsilon ₁ 、ε ₂ For example, the material and the production method of the first and second release films can be adjusted.

The first release film and the second release film may be formed with a maximum strain epsilon of the first release film ₁ Maximum stress relative to the second release filmBecome epsilon ₂ Ratio of (epsilon) ₁ /ε ₂ ) So as to be 1.2 or more. When such a combination of the first release film and the second release film is used, the occurrence of unintended separation tends to be more prevented. In some embodiments, the ratio (ε) ₁ /ε ₂ ) For example, it may be 1.4 or more, or 1.5 or more. Ratio (epsilon) ₁ /ε ₂ ) The upper limit of (b) is not particularly limited, and may be, for example, 7.0 or less, or 5.0 or less.

(Peel force)

In the release film-equipped adhesive sheet disclosed herein, the peeling force R from the second release film is ₂ Subtracting the peel force R of the first release film ₁ And the difference in peel force (R) defined in the form of the value obtained ₂ -R ₁ ) There is no particular limitation. Poor peeling force (R) ₂ -R ₁ ) The pressure-sensitive adhesive sheet can be used in a range where unintended separation of the pressure-sensitive adhesive sheet can be prevented as appropriate depending on the purpose and the mode of use. Difference in Peel force (R) ₂ -R ₁ ) For example, it may be 1.0N/50mm or less, 0.8N/50mm or less, 0.5N/50mm or less, or 0.3N/50mm or less. In addition, the above peeling force difference (R) ₂ -R ₁ ) For example, it may be 1.00N/50mm or less, or may be 0.80N/50mm or less, or may be 0.50N/50mm or less, or may be 0.30N/50mm or less, or may be 0.20N/50mm or less, or may be 0.10N/50mm or less.

Some preferred embodiments of the pressure-sensitive adhesive sheet with a release film have poor release force (R) ₂ -R ₁ ) For example, it may be 0.25N/50mm or less, 0.2N/50mm or less, 0.15N/50mm or less, or 0.1N/50mm or less. May be 0.07N/50mm or less, or may be 0.05N/50mm or less. If the difference in peeling force (R) is utilized ₂ -R ₁ ) Such a small release film-equipped pressure-sensitive adhesive sheet can reduce the peeling force of the second release film. The first pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet held on the second release film is adhered to the surface of an adherend (which may be a releasable surface such as a process liner or a surface having low adhesiveness or poor adhesiveness such as a member having low polarity) by reducing the peel force of the second release film, and the pressure-sensitive adhesive sheet is transferredThe transferability to the adherend is improved. In particular, in the case of a pressure-sensitive adhesive sheet with a release film used to transfer the pressure-sensitive adhesive sheet to a process liner by attaching a first pressure-sensitive adhesive surface to the process liner, the release force of the second release film is reduced, whereby the pressure-sensitive adhesive sheet can be transferred to the process liner even if the release force of the process liner is further reduced. From the viewpoint of transferability when the pressure-sensitive adhesive sheet on the process liner is transferred to the surface of an adherend (which may be the surface of a subsequent process liner or the surface of a member that is difficult to adhere), it is advantageous to use a process liner having a lower release force.

Peeling force R of first peeling film ₁ There is no particular limitation. Peel force R from the suppression second release film ₂ So that the peeling force R of the first release film can be easily improved ₁ Usually, it is preferably 3.0N/50mm or less, more preferably 2.0N/50mm or less, and still more preferably 1.5N/50mm or less. In some embodiments, the first release film has a release force R ₁ For example, it may be 1.0N/50mm or less, 0.7N/50mm or less, 0.5N/50mm or less, 0.3N/50mm or less, or 0.2N/50mm or less. Further, the peeling force R of the first peeling film ₁ For example, it may be 3.00N/50mm or less, or 2.00N/50mm or less, 1.50N/50mm or less, 1.00N/50mm or less, 0.70N/50mm or less, 0.50N/50mm or less, 0.30N/50mm or less, or 0.20N/50mm or less. Peeling force R of first peeling film ₁ The lower limit of (b) is not particularly limited, but is usually preferably 0.01N/50mm or more from the viewpoint of properly exerting the protective property of the first adhesive surface. In some embodiments, the peel force R ₁ For example, it may be 0.05N/50mm or more, 0.08N/50mm or more, or 0.1N/50mm or more. Peeling force R ₁ It may be 0.10N/50mm or more.

Peeling force R of second peeling film ₂ There is no particular limitation. The peeling force R of the second release film from the viewpoint of improving transferability of the pressure-sensitive adhesive sheet held on the second release film to an adherend ₂ Usually, it is preferably 5.0N/50mm or less, more preferably 3.0N/50mm or less,More preferably 2.0N/50mm or less. In some embodiments, the second release film has a release force R ₂ For example, it may be 1.5N/50mm or less, 1.0N/50mm or less, 0.6N/50mm or less, 0.4N/50mm or less, or 0.3N/50mm or less. Further, the peeling force R of the second peeling film ₂ For example, it may be 5.00N/50mm or less, or 3.00N/50mm or less, 2.00N/50mm or less, 1.50N/50mm or less, 1.00N/50mm or less, 0.60N/50mm or less, 0.40N/50mm or less, or 0.30N/50mm or less. Peeling force R of second peeling film ₂ The lower limit of (b) is not particularly limited, but is usually preferably 0.01N/50mm or more from the viewpoint of properly exerting the protective property of the second adhesive surface. In some embodiments, the peel force R ₂ For example, it may be 0.05N/50mm or more, 0.08N/50mm or more, 0.10N/50mm or more, or 0.12N/50mm or more.

In addition, the peeling force was poor (R) ₂ -R ₁ ) The value of (b) is not limited to a positive number. The difference in peeling force (R) is small as long as it prevents or suppresses the occurrence of unintended separation when the adhesive sheet is left on the second release film and the first release film is removed from the first adhesive surface of the adhesive sheet ₂ -R ₁ ) The value of (B) may be 0N/50mm or less than 0N/50 mm.

The above peel force (N/50mm) was measured by the following method. That is, a single-sided pressure-sensitive adhesive tape (a single-sided pressure-sensitive adhesive tape having an acrylic pressure-sensitive adhesive layer on a polyester substrate, trade name "No. 31B", substrate thickness of 25 μm, total thickness of 53 μm, and width of 19mm) manufactured by ritto electrical corporation was attached to the release surface of a release film to be measured under an environment of 23 ℃ and 50% RH, and after leaving for 24 hours with a load of 5kg, the film was released under conditions of a tensile rate of 0.3 m/min and a release angle of 180 degrees using a universal tensile tester. The peel force (N/50mm) was determined by converting the peel force (N/19mm) observed at this time into a value of 50mm per width. The peeling force of each of the release films and the transfer property evaluation release film used in examples described later was measured by the above-described method. The peeling force can be adjusted by the material and thickness of the peeling film base, the kind of the peeling agent used for forming the peeling treatment layer, the thickness of the peeling treatment layer, the forming conditions, and the like.

The thickness of the release film is not particularly limited. From the viewpoint of achieving both strength and flexibility, a release film having a thickness of about 10 μm to about 500 μm can be preferably used.

In some embodiments, the thickness t of the first release film ₁ For example, it may be 20 μm or more, 30 μm or more, or 45 μm or more. By increasing the thickness t of the first release film ₁ Thus, the handling property tends to be improved. In addition, the thickness t of the first release film is set so as not to unnecessarily increase the thickness of the release film-attached pressure-sensitive adhesive sheet ₁ For example, it may be 250 μm or less, 150 μm or less, or 100 μm or less.

In some embodiments, the thickness t of the second release film ₂ For example, it may be 10 μm or more, 20 μm or more, 30 μm or more, or 35 μm or more. By increasing the thickness t of the second release film ₂ Thus, the handling property tends to be improved. In addition, for example, in the case of a pressure-sensitive adhesive sheet with a release film usable in a system of transferring the pressure-sensitive adhesive sheet on the second release film to a releasable surface (a releasable surface of a process liner or the like) or a system of attaching the pressure-sensitive adhesive sheet to an adherend difficult to adhere, from the viewpoint of improving transferability, the thickness t of the second release film ₂ For example, it may be 150 μm or less, 100 μm or less, 80 μm or less, 60 μm or less, or 45 μm or less. Alternatively, for example, in the case of a pressure-sensitive adhesive sheet with a release film which is used in a system in which the first pressure-sensitive adhesive surface is accurately bonded to the final adherend, the thickness t of the second release film is set to the thickness t of the pressure-sensitive adhesive sheet with a release film for the application in which the shape retention property and the dimensional stability of the pressure-sensitive adhesive sheet held on the second release film are important ₂ For example, it may be 70 μm or more, 120 μm or more, or 160 μm or more.

Thickness t of first peeling film ₁ Thickness t of the second release film ₂ The relationship (c) is not particularly limited. Thickness t of first peeling film ₁ Relative to the firstThickness t of double-peeling film ₂ Ratio of (d), i.e. thickness ratio (t) ₁ /t ₂ ) For example, the range may be about 0.3 to 10. The thickness ratio (t) is set so that the pressure-sensitive adhesive sheet with a release film can be used in a mode of transferring the pressure-sensitive adhesive sheet on the second release film to a releasable surface or a mode of attaching an adherend difficult to be adhered ₁ /t ₂ ) For example, the concentration may be about 1 to 10, and is preferably more than 1 and not more than 5, and may be more than 1 and not more than 3. In addition, the above thickness ratio (t) is set for the pressure-sensitive adhesive sheet with a release film for applications where shape retention and dimensional stability of the pressure-sensitive adhesive sheet held on the second release film are important ₁ /t ₂ ) For example, the range may be about 0.3 to 3, or about 0.5 to 2.

< adhesive layer >

In the technique disclosed herein, the type of the adhesive constituting the adhesive layer is not particularly limited. For example, the pressure-sensitive adhesive layer may be a pressure-sensitive adhesive layer composed of 1 or 2 or more kinds of pressure-sensitive adhesives selected from known various pressure-sensitive adhesives such as acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives (natural rubber-based, synthetic rubber-based, and mixed systems thereof), silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, urethane pressure-sensitive adhesives, polyether pressure-sensitive adhesives, polyamide pressure-sensitive adhesives, and fluorine pressure-sensitive adhesives. Here, the acrylic adhesive refers to an adhesive containing a (meth) acrylic polymer as a base polymer (a main component in the polymer component, that is, a component having a content of more than 50% by weight). The same applies to rubber-based adhesives and other adhesives.

From the viewpoint of transparency, weather resistance, and the like, a preferable pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer containing an acrylic pressure-sensitive adhesive in a proportion of 50 wt% or more, more preferably 70 wt% or more, and still more preferably 90 wt% or more. The content of the acrylic pressure-sensitive adhesive may be more than 98% by weight, or may be a pressure-sensitive adhesive layer substantially composed of the acrylic pressure-sensitive adhesive.

(acrylic Polymer)

Although not particularly limited, in one preferable embodiment of the technology disclosed herein, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive contain an acrylic polymer as a base polymer. The acrylic polymer is preferably a polymer of a monomer raw material containing an alkyl (meth) acrylate as a main monomer and may further contain a secondary monomer copolymerizable with the main monomer. Here, the main monomer means a component contained in an amount of more than 50% by weight in the above monomer raw materials.

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be suitably used.

CH ₂ ＝C(R ¹ )COOR ² (1)

Here, R in the above formula (1) ¹ Is a hydrogen atom or a methyl group. In addition, R ² Is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of carbon atoms may be referred to as "C _1-20 ". ). From the viewpoint of storage modulus of the binder, R is preferred ² Is C _1-14 Alkyl (meth) acrylate of a chain alkyl group(s), more preferably R ² Is C _1-10 The alkyl (meth) acrylate of a chain alkyl group(s), particularly preferably R ² Alkyl (meth) acrylates which are butyl or 2-ethylhexyl.

As R ² Is C _1-20 Examples of the alkyl (meth) acrylate having a chain alkyl group of (a) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, dodecyl (meth) acrylate, and the like, Pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, and a salt thereof) Nonadecyl acrylate, eicosyl (meth) acrylate, and the like. These alkyl (meth) acrylates may be used alone in 1 kind or in combination of 2 or more kinds. As particularly preferred alkyl (meth) acrylates, n-Butyl Acrylate (BA) and 2-ethylhexyl acrylate (2EHA) may be mentioned.

The technique disclosed herein can be preferably carried out in such a manner that the monomer component constituting the acrylic polymer contains at least one of BA and 2EHA, and the total amount of BA and 2EHA in the alkyl (meth) acrylate contained in the monomer component is 75 wt% or more (usually 85 wt% or more, for example 90 wt% or more, and further 95 wt% or more). The technique disclosed herein can be implemented, for example, in an embodiment in which the alkyl (meth) acrylate contained in the monomer component is BA itself, in an embodiment in which the alkyl (meth) acrylate is 2EHA itself, in an embodiment in which the alkyl (meth) acrylate is formed of BA and 2EHA, or the like.

When the monomer component contains BA and 2EHA, the weight ratio of BA to 2EHA (BA/2EHA) is not particularly limited, and may be, for example, 1/99 or more and 99/1 or less. In one preferred embodiment, the BA/2EHA may be 40/60 or less (for example, 1/99 to 40/60) or 20/80 or less, or 10/90 or less (for example, 1/99 to 10/90).

In a preferred embodiment of the technique disclosed herein, an acidic group-containing monomer is used as a monomer copolymerizable with an alkyl (meth) acrylate as a main monomer. The acid group-containing monomer can exert an improvement in the aggregating ability based on its polarity and a good binding force to a polar adherend. When a crosslinking agent such as an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent is used, the acidic group (typically, a carboxyl group) serves as a crosslinking point of the acrylic polymer. By these actions, it is possible to preferably design an acrylic polymer that increases the strength of the adhesive layer itself, suitable for suppressing unintended separation.

As the acid group-containing monomer, a carboxyl group-containing monomer is preferably used. Examples of the carboxyl group-containing monomer include ethylenically unsaturated monocarboxylic acids such as Acrylic Acid (AA), methacrylic acid (MAA), carboxyethyl (meth) acrylate, crotonic acid, and isocrotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid, and anhydrides thereof (maleic anhydride, itaconic anhydride, and the like). In addition, the acid group-containing monomer may be a monomer having a metal salt (e.g., an alkali metal salt) having a carboxyl group. Among them, AA and MAA are preferable, and AA is more preferable. When 1 or 2 or more types of acid group-containing monomers are used, the ratio of AA in the acid group-containing monomers is preferably 50% by weight or more, more preferably 70% by weight or more, and still more preferably 90% by weight or more. In a particularly preferred embodiment, the acidic group-containing monomer is substantially composed of only AA.

The content of the acid group-containing monomer (typically, the carboxyl group-containing monomer) in the monomer component (in other words, the copolymerization ratio of the acid group-containing monomer in the acrylic polymer) may be, for example, 0.5% by weight or more, 1% by weight or more, or 3% by weight or more. In some embodiments, the content of the acid group-containing monomer may be, for example, 5 wt% or more, or 8 wt% or more, or 10 wt% or more, from the viewpoint of easily obtaining a higher cohesive force. In addition, the content of the acid group-containing monomer may be, for example, 15 wt% or less, or 13 wt% or less, or 12 wt% or less, from the viewpoint of quickly achieving a good adhesion state to an adherend.

In the technique disclosed herein, as the secondary monomer copolymerizable with the alkyl (meth) acrylate as the main monomer, a copolymerizable monomer other than the carboxyl group-containing monomer may be used. As the auxiliary monomer, for example, the following functional group-containing monomers can be used.

Hydroxyl group-containing monomer: hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; polypropylene glycol mono (meth) acrylate.

Amide group-containing monomer: such as (meth) acrylamide, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide.

Amino group-containing monomers: for example aminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, tert-butylaminoethyl (meth) acrylate.

Monomer having epoxy group: such as glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether.

A cyano group-containing monomer: such as acrylonitrile, methacrylonitrile.

A ketone group-containing monomer: such as diacetone (meth) acrylamide, diacetone (meth) acrylate, methyl vinyl ketone, ethyl vinyl ketone, allyl acetoacetate, vinyl acetoacetate.

Monomer having nitrogen atom-containing ring: such as N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N- (meth) acryloylmorpholine.

Alkoxysilyl group-containing monomer: for example, 3- (meth) acryloyloxypropyltrimethoxysilane, 3- (meth) acryloyloxypropyltriethoxysilane, 3- (meth) acryloyloxypropylmethyldimethoxysilane, 3- (meth) acryloyloxypropylmethyldiethoxysilane.

The above-mentioned functional group-containing monomers may be used singly in 1 kind or in combination in 2 or more kinds. When the monomer component constituting the acrylic polymer contains a functional group-containing monomer, the ratio of the functional group-containing monomer in the monomer component is appropriately determined depending on the required performance of the adhesive sheet. The ratio of the functional group-containing monomer (copolymerization ratio) is preferably about 0.1% by weight or more (for example, about 0.5% by weight or more, usually about 1% by weight or more) in the monomer component. The upper limit is preferably about 40 wt% or less (e.g., 30 wt% or less, usually 20 wt% or less). In a more preferred embodiment, the ratio of the functional group-containing monomer other than the acid group-containing monomer is, for example, 10 wt% or less, and preferably 5 wt% or less, and may be 1 wt% or less. The monomer component constituting the acrylic polymer may be substantially free of a functional group-containing monomer other than the above-mentioned acidic group-containing monomer.

As the monomer component constituting the acrylic polymer, other copolymerization components than the above-mentioned acid group-containing monomer and other auxiliary monomers may be used for the purpose of improving the cohesive force of the acrylic polymer, etc. Examples of the copolymerization component include: vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; aromatic vinyl compounds such as styrene, substituted styrene (α -methylstyrene, etc.), vinyl toluene, etc.; cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate, cyclopentyl (meth) acrylate, and isobornyl (meth) acrylate; aromatic ring-containing (meth) acrylates such as aryl (meth) acrylates (e.g., phenyl (meth) acrylate), aryloxyalkyl (meth) acrylates (e.g., phenoxyethyl (meth) acrylate), and arylalkyl (meth) acrylates (e.g., benzyl (meth) acrylate); olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; isocyanate group-containing monomers such as 2- (meth) acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether.

The amount of the other copolymerizable component is not particularly limited as long as it is appropriately selected depending on the purpose and use, and is usually preferably 10% by weight or less of the monomer component. For example, when a vinyl ester monomer (e.g., vinyl acetate) is used as the other copolymerization component, the content thereof may be, for example, about 0.1% by weight or more (usually about 0.5% by weight or more) and about 20% by weight or less (usually about 10% by weight or less) of the monomer component.

The acrylic polymer may contain, as another monomer component, a polyfunctional monomer having a polymerizable functional group (typically, a radical polymerizable functional group) having an unsaturated double bond such as at least 2 (meth) acryloyl groups or vinyl groups. By using a polyfunctional monomer as a monomer component, the cohesive force of the adhesive layer can be increased. Multifunctional monomers may be used as crosslinking agents.

Examples of the polyfunctional monomer include esters of polyhydric alcohols such as ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1, 2-ethylene glycol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 12-dodecanol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, and (meth) acrylic acid; allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, and the like. Suitable examples of these include trimethylolpropane tri (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, and dipentaerythritol hexa (meth) acrylate. Among them, 1, 6-hexanediol di (meth) acrylate is a preferable example. The polyfunctional monomer may be used alone in 1 kind or in combination of 2 or more kinds. From the viewpoint of reactivity and the like, a polyfunctional monomer having 2 or more acryloyl groups is generally preferable.

The amount of the polyfunctional monomer to be used is not particularly limited, and can be suitably set in such a manner as to achieve the intended use of the polyfunctional monomer. From the viewpoint of achieving both initial adhesiveness and aggregability in a well-balanced manner, the amount of the polyfunctional monomer used may be about 3 wt% or less, preferably about 2 wt% or less, and more preferably about 1 wt% or less (for example, about 0.5 wt% or less) of the monomer component. The lower limit of the amount of the polyfunctional monomer used is not particularly limited as long as it is more than 0% by weight. The effect of the polyfunctional monomer in use can be suitably exhibited by setting the amount of the polyfunctional monomer to about 0.001% by weight or more (for example, about 0.01% by weight or more) of the monomer component.

The composition of the monomer component constituting the acrylic polymer is suitably designed so that the glass transition temperature (Tg) of the acrylic polymer is about-15 ℃ or lower (for example, about-70 ℃ or higher and-15 ℃ or lower). Here, the Tg of the acrylic polymer refers to the Tg determined by the Fox equation based on the composition of the monomer components. The Fox formula is a relational expression between Tg of a copolymer and glass transition temperature Tgi of a homopolymer obtained by homopolymerizing monomers constituting the copolymer.

1/Tg＝Σ(Wi/Tgi)

In the above Fox formula, Tg represents the glass transition temperature (unit: K) of the copolymer, Wi represents the weight fraction (weight-based copolymerization ratio) of the monomer i in the copolymer, and Tgi represents the glass transition temperature (unit: K) of the homopolymer of the monomer i.

The glass transition temperature of the homopolymer used for calculating Tg was the value described in the publicly known data. For example, the following values are used for the monomers listed below as the glass transition temperatures of the homopolymers of the monomers.

Regarding the glass transition temperature of a homopolymer of a monomer other than those exemplified above, the values described in "Polymer Handbook" (3 rd edition, John Wiley & Sons, inc.,1989) were used. The highest value is used for monomers having various values described in this document. As the monomer having no description of the glass transition temperature of the homopolymer in the above-mentioned document, a value obtained by the method described in Japanese patent laid-open No. 2007-51271 is used.

Although not particularly limited, the acrylic polymer has a Tg of favorably about-25 ℃ or lower, preferably about-35 ℃ or lower, more preferably about-40 ℃ or lower, still more preferably-45 ℃ or lower, and particularly preferably-50 ℃ or lower from the viewpoint of adhesiveness. In addition, the Tg of the acrylic polymer is usually about-75 ℃ or higher, preferably about-70 ℃ or higher, from the viewpoint of the cohesive force of the pressure-sensitive adhesive layer. The techniques disclosed herein may preferably be implemented in such a way that the Tg of the acrylic polymer is from about-65 ℃ or higher to about-40 ℃ or lower (e.g., from about-65 ℃ or higher to about-45 ℃ or lower). In some embodiments, the acrylic polymer may have a Tg of about-65 ℃ or greater and about-55 ℃ or less. The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (i.e., the kind and amount ratio of the monomers used in the synthesis of the polymer).

The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and may be, for example, about 10X 10 ⁴ Above and 500X 10 ⁴ The following. From the viewpoint of aggregability, the Mw is usually about 30X 10 ⁴ Above, set to about 45 × 10 ⁴ Above (e.g. about 65X 10) ⁴ The above) are suitable. In a preferred embodiment, the Mw of the acrylic polymer may be, for example, 70 × 10 from the viewpoint of improving the tensile durability (difficulty in twisting off) of the pressure-sensitive adhesive layer improved in the aggregation property by the high molecular weight material ⁴ Above, it may be about 75 × 10 ⁴ Above, about 90X 10 ⁴ Above, or about 95 × 10 ⁴ The above. Further, the Mw is usually 300X 10 ⁴ The following (more preferably about 200X 10) ⁴ Hereinafter, for example, about 150X 10 ⁴ The following) is suitable. The Mw of the acrylic polymer may be about 140X 10 ⁴ The following.

The Mw is determined from a value obtained by GPC (gel permeation chromatography) in terms of standard polystyrene. As the GPC apparatus, for example, the model name "HLC-8320 GPC" (column: TSK gel GMH-H (S), manufactured by Tosoh corporation) can be used.

< adhesive composition >

The pressure-sensitive adhesive layer disclosed herein can be formed using a pressure-sensitive adhesive composition containing a monomer component having the above-described composition in the form of a polymer, an unpolymerized product (i.e., a product in which polymerizable functional groups are not reacted), or a mixture thereof. The adhesive composition may be in various forms such as: a composition (solvent-based adhesive composition) in which an adhesive (adhesive component) is contained in an organic solvent; a composition in which a binder is dispersed in an aqueous solvent (water-dispersible binder composition); a composition prepared so as to form a pressure-sensitive adhesive by curing with an active energy ray such as an ultraviolet ray or a radiation ray (active energy ray-curable pressure-sensitive adhesive composition); and hot melt adhesive compositions which form an adhesive when applied in a molten state under heating and cooled to around room temperature. The technique disclosed herein can be particularly preferably carried out in a mode of having a pressure-sensitive adhesive layer formed of a solvent-based pressure-sensitive adhesive composition or an active energy ray-curable pressure-sensitive adhesive composition from the viewpoint of adhesive properties and the like.

In the present specification, the "active energy ray" refers to an energy ray having energy capable of causing a chemical reaction such as a polymerization reaction, a crosslinking reaction, and decomposition of an initiator. Examples of the active energy rays include light such as ultraviolet rays, visible rays, and infrared rays; radiation rays such as α rays, β rays, γ rays, electron rays, neutron rays, and X rays.

The adhesive composition typically contains at least a part of the monomer components of the composition in the form of a polymer (may be a part of the monomer species or a part of the weight). The polymerization method for forming the polymer is not particularly limited, and various conventionally known polymerization methods can be appropriately used. For example, thermal polymerization such as solution polymerization, emulsion polymerization, and bulk polymerization (typically, in the presence of a thermal polymerization initiator); photopolymerization by irradiation with light such as ultraviolet light (typically, in the presence of a photopolymerization initiator); radiation polymerization by irradiation with radiation such as β -rays and γ -rays. Among them, solution polymerization and photopolymerization are preferable. In these polymerization methods, the mode of polymerization is not particularly limited, and the polymerization can be carried out by appropriately selecting conventionally known monomer supply methods, polymerization conditions (temperature, time, pressure, light irradiation amount, radiation irradiation amount, and the like), materials used other than the monomers (polymerization initiator, surfactant, and the like), and the like.

For example, in a preferred embodiment, the acrylic polymer can be synthesized by a solution polymerization method. The solution polymerization described above can provide a polymerization reaction solution in which the acrylic polymer is dissolved in an organic solvent. The pressure-sensitive adhesive layer in the technique disclosed herein may be formed from a pressure-sensitive adhesive composition containing the above-mentioned polymerization reaction liquid or an acrylic polymer solution obtained by subjecting the reaction liquid to an appropriate post-treatment. As the acrylic polymer solution, a solution obtained by adjusting the polymerization reaction solution to an appropriate viscosity (concentration) as necessary can be used. Alternatively, an acrylic polymer solution prepared by synthesizing an acrylic polymer by a polymerization method other than solution polymerization (e.g., emulsion polymerization, photopolymerization, bulk polymerization, etc.) and dissolving the acrylic polymer in an organic solvent may also be used.

As a method of supplying the monomer in the solution polymerization, a one-shot charging method of supplying all the monomer raw materials at once, a continuous supply (dropwise addition) method, a batch supply (dropwise addition) method, and the like can be suitably employed. The polymerization temperature may be suitably selected depending on the kind of the monomer and the solvent used, the kind of the polymerization initiator, and the like, and may be, for example, about 20 to 170 ℃ (usually about 40 to 140 ℃). In a preferred embodiment, the polymerization temperature may be set to about 75 ℃ or lower (more preferably about 65 ℃ or lower, for example, about 45 ℃ to 65 ℃).

The solvent (polymerization solvent) used for the solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds (for example, aromatic hydrocarbons) selected from toluene, xylene, and the like; acetates such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane and methylcyclohexane; halogenated alkanes such as 1, 2-dichloroethane; lower alcohols (e.g., monohydric alcohols having 1 to 4 carbon atoms) such as isopropyl alcohol; ethers such as t-butyl methyl ether; ketones such as methyl ethyl ketone and acetone; and the like, or a mixed solvent of 2 or more.

On the other hand, in the case where an active energy ray-curable adhesive composition (typically, a photocurable adhesive composition) is used as another embodiment of the technology disclosed herein, it is preferable that the active energy ray-curable adhesive composition does not substantially contain an organic solvent from the viewpoint of environmental hygiene and the like. For example, adhesive compositions having an organic solvent content of about 5 wt% or less (more preferably about 3 wt% or less, e.g., about 0.5 wt% or less) are preferred. Further, as described below, since the pressure-sensitive adhesive layer is suitable for forming a form in which a liquid film of the pressure-sensitive adhesive composition is cured between the release surfaces of the pair of release films, a pressure-sensitive adhesive composition substantially free of a solvent (including an organic solvent and an aqueous solvent) is preferred. For example, an adhesive composition having a solvent content of about 5 wt% or less (more preferably about 3 wt% or less, for example about 0.5 wt% or less) is preferred. Here, the solvent refers to a volatile component to be removed in the process of forming the pressure-sensitive adhesive layer, that is, a volatile component which is not intended to be a constituent component of the finally formed pressure-sensitive adhesive layer.

In the polymerization, a known or conventional thermal polymerization initiator or photopolymerization initiator can be used depending on the polymerization method, polymerization system, and the like. Such polymerization initiators may be used in 1 kind alone or in appropriate combination of 2 or more kinds.

The thermal polymerization initiator is not particularly limited, and examples thereof include azo polymerization initiators, peroxide initiators, redox initiators comprising a combination of a peroxide and a reducing agent, and substituted ethane initiators. More specifically, examples of the azo initiators include 2,2 ' -Azobisisobutyronitrile (AIBN), 2 ' -azobis (2-methylpropionamidine) disulfate, 2 ' -azobis (2-amidinopropane) dihydrochloride, 2 ' -azobis [2- (5-methyl-2-imidazolin-2-yl) propane ] dihydrochloride, 2 ' -azobis (N, N ' -dimethyleneisobutylamidine), and 2,2 ' -azobis [ N- (2-carboxyethyl) -2-methylpropionamidine ] hydrate; persulfates such as potassium persulfate and ammonium persulfate; peroxide initiators such as Benzoyl Peroxide (BPO), t-butyl hydroperoxide and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; redox initiators such as a combination of a persulfate and sodium bisulfite and a combination of a peroxide and sodium ascorbate; and the like, but are not limited thereto. The thermal polymerization is preferably carried out at a temperature of about 20 to 100 ℃ C (typically 40 to 80 ℃ C.).

The photopolymerization initiator is not particularly limited, and for example, ketal photopolymerization initiator, acetophenone photopolymerization initiator, benzoin ether photopolymerization initiator, acylphosphine oxide photopolymerization initiator, α -ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactive oxime photopolymerization initiator, benzoin photopolymerization initiator, benzil photopolymerization initiator, benzophenone photopolymerization initiator, thioxanthone photopolymerization initiator and the like can be used.

Specific examples of the ketal-based photopolymerization initiator include 2, 2-dimethoxy-1, 2-diphenylethan-1-one (for example, product name "Irgacure 651" manufactured by BASF corporation), and the like.

Specific examples of the acetophenone photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone (for example, trade name "Irgacure 184" manufactured by BASF), 4-phenoxy dichloroacetophenone, 4-tert-butyl dichloroacetophenone, 1- [4- (2-hydroxyethoxy) -phenyl ] -2-hydroxy-2-methyl-1-propan-1-one (for example, trade name "Irgacure 2959" manufactured by BASF), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (for example, trade name "Darocure 1173" manufactured by BASF), methoxyacetophenone, and the like.

Specific examples of the benzoin ether-based photopolymerization initiator include benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether and benzoin isobutyl ether, and substituted benzoin ethers such as anisole methyl ether.

Specific examples of the acylphosphine oxide-based photopolymerization initiator include bis (2,4, 6-trimethylbenzoyl) phenylphosphine oxide (for example, trade name "Irgacure 819" manufactured by BASF), bis (2,4, 6-trimethylbenzoyl) -2, 4-di-n-butoxyphenylphosphine oxide, 2,4, 6-trimethylbenzoyldiphenylphosphine oxide (for example, trade name "Lucirin TPO" manufactured by BASF), bis (2, 6-dimethoxybenzoyl) -2,4, 4-trimethylpentylphosphine oxide, and the like.

Specific examples of the α -ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1- [4- (2-hydroxyethyl) phenyl ] -2-methylpropan-1-one. Specific examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride and the like. Specific examples of the optically active oxime-based photopolymerization initiator include 1-phenyl-1, 1-propanedione-2- (O-ethoxycarbonyl) oxime and the like. Specific examples of the benzoin-based photopolymerization initiator include benzoin and the like. Specific examples of the benzil-based photopolymerization initiator include benzil and the like.

Specific examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3' -dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α -hydroxycyclohexylphenylketone, and the like.

Specific examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2, 4-dimethylthioxanthone, isopropylthioxanthone, 2, 4-dichlorothioxanthone, 2, 4-diethylthioxanthone, isopropylthioxanthone, 2, 4-diisopropylthioxanthone, dodecylthioxanthone, and the like.

The amount of the thermal polymerization initiator or the photopolymerization initiator to be used is not particularly limited, and may be a usual amount in accordance with the polymerization method, polymerization system, or the like. For example, the polymerization initiator may be used in an amount of about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, for example about 0.01 to 1 part by weight) based on 100 parts by weight of the monomer to be polymerized.

(adhesive composition comprising monomer component in the form of complete polymer)

The adhesive composition of a preferred embodiment contains the monomer components of the adhesive composition in the form of a complete polymer. Such adhesive compositions may be, for example: a solvent-based pressure-sensitive adhesive composition containing an acrylic polymer as a complete polymer of a monomer component in an organic solvent, and a water dispersion-type pressure-sensitive adhesive composition in which the acrylic polymer is dispersed in an aqueous solvent. In the present specification, "complete polymer" means that the polymerization conversion rate exceeds 95% by weight.

(adhesive composition comprising a Polymer of monomer Components and an unpolymerized)

Another preferred embodiment of the adhesive composition comprises a polymerization reaction of a monomer mixture comprising at least a portion of the monomer component (starting monomer) of the composition. Typically, a part of the monomer component is contained in the form of a polymer, and the remaining monomer is contained in the form of an unreacted monomer. The polymerization reactants of the above monomer mixture may be prepared by polymerizing at least a portion of the monomer mixture.

The polymerization reactant is preferably a partial polymer of the monomer mixture. Such a partial polymer is a mixture of a polymer derived from the above monomer mixture and an unreacted monomer, and typically exhibits a slurry state (viscous liquid state). Hereinafter, the partial polymer having such a property may be referred to as "monomer slurry" or simply "slurry".

The polymerization method for obtaining the above-mentioned polymerization reaction product is not particularly limited, and various polymerization methods such as those described above can be appropriately selected and used. From the viewpoint of efficiency and simplicity, a photopolymerization method is preferably employed. By using photopolymerization, the polymerization conversion rate of the monomer mixture can be easily controlled by polymerization conditions such as the amount of light irradiation (light amount).

The polymerization conversion rate (monomer conversion) of the monomer mixture in the above partial polymer is not particularly limited. The polymerization conversion rate may be, for example, about 70 wt% or less, and preferably about 60 wt% or less. From the viewpoint of ease of preparation, coatability, and the like of the adhesive composition containing the partial polymer, the polymerization conversion rate is usually preferably about 50% by weight or less, and preferably about 40% by weight or less (for example, about 35% by weight or less). The lower limit of the polymerization conversion rate is not particularly limited, but is typically about 1 wt% or more, and usually about 5 wt% or more is suitable.

The adhesive composition containing a partial polymer of the above monomer mixture can be easily obtained, for example, by partially polymerizing a monomer mixture containing all raw material monomers by an appropriate polymerization method (e.g., photopolymerization method). The pressure-sensitive adhesive composition containing the above partial polymer may be blended with other components (for example, a photopolymerization initiator, a polyfunctional monomer, a crosslinking agent, an acrylic oligomer described later, and the like) used as needed. The method for compounding such other components is not particularly limited, and for example, they may be contained in the monomer mixture in advance or may be added to the partial polymer.

The adhesive composition disclosed herein may be in a form in which a complete polymer of a monomer mixture containing a part of the types of monomers in the monomer components (raw material monomers) is dissolved in the remaining types of monomers or a partial polymer thereof. Adhesive compositions of this morphology are also included in the example of polymeric and non-polymeric adhesive compositions containing monomeric components.

As a curing method (polymerization method) in forming the adhesive from the adhesive composition containing the polymer of the monomer component and the non-polymer as described above, a photopolymerization method can be preferably employed. As for the adhesive composition containing the polymerization reactant prepared by the photopolymerization method, the photopolymerization method is particularly suitably employed as the curing method thereof. Since the polymerization reaction product obtained by the photopolymerization method already contains a photopolymerization initiator, photocuring can be performed without adding a new photopolymerization initiator when the adhesive composition containing the polymerization reaction product is further cured to form an adhesive. Alternatively, the pressure-sensitive adhesive composition may have a composition in which a photopolymerization initiator is added to a polymerization reaction product prepared by a photopolymerization method as needed. The additional photopolymerization initiator may be the same as or different from the photopolymerization initiator used to prepare the polymerization reaction product. The adhesive composition prepared by a method other than photopolymerization can be made photocurable by adding a photopolymerization initiator. The photocurable adhesive composition has an advantage that even a thick adhesive layer can be easily formed. In a preferred embodiment, photopolymerization in forming the adhesive from the adhesive composition can be performed by ultraviolet irradiation. The ultraviolet irradiation may be performed using a known high-pressure mercury lamp, low-pressure mercury lamp, metal halide lamp, or the like.

(crosslinking agent)

The adhesive composition (preferably, solvent-based adhesive composition) used for forming the adhesive layer preferably contains a crosslinking agent as an optional component. By including the crosslinking agent, the cohesive force of the adhesive can be improved. Increasing the cohesive force of the adhesive is advantageous from the viewpoint of preventing unintended separation. The pressure-sensitive adhesive layer in the technique disclosed herein may contain the crosslinking agent in a form after the crosslinking reaction, a form before the crosslinking reaction, a form in which the partial crosslinking reaction has been carried out, an intermediate form or a composite form thereof, or the like. The crosslinking agent is usually contained exclusively in the adhesive layer in a form after the crosslinking reaction.

The kind of the crosslinking agent is not particularly limited, and can be suitably selected from conventionally known crosslinking agents and used. Examples of such a crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a melamine-based crosslinking agent, a carbodiimide-based crosslinking agent, a hydrazine-based crosslinking agent, an amine-based crosslinking agent, a peroxide-based crosslinking agent, a metal chelate-based crosslinking agent, a metal alkoxide-based crosslinking agent, and a metal salt-based crosslinking agent. The crosslinking agent may be used alone in 1 kind or in combination of 2 or more kinds. Examples of the crosslinking agent that can be preferably used in the technology disclosed herein include isocyanate-based crosslinking agents and epoxy-based crosslinking agents.

As the epoxy crosslinking agent, a compound having 2 or more epoxy groups in 1 molecule can be used without particular limitation. Preferably an epoxy crosslinking agent having 3 to 5 epoxy groups in 1 molecule. The epoxy crosslinking agent may be used alone in 1 kind or in combination of 2 or more kinds. Specific examples of the epoxy-based crosslinking agent include N, N' -tetraglycidyl-m-xylylenediamine, 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, 1, 6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether. As the commercial product of the epoxy crosslinking agent, there may be mentioned trade name "TETRAD-C" and trade name "TETRAD-X" manufactured by Mitsubishi gas chemical Co., Ltd., trade name "EPICLON CR-5L" manufactured by DIC Co., Ltd., trade name "DENACOL EX-512" manufactured by Nagase ChemteX Corporation, trade name "TEPIC-G" manufactured by Nissan chemical industries, Ltd., and the like.

In the embodiment using the epoxy crosslinking agent, the amount thereof is not particularly limited. The amount of the epoxy crosslinking agent to be used may be, for example, more than 0 part by weight and not more than about 1 part by weight (preferably about 0.001 to 0.5 part by weight) based on 100 parts by weight of the acrylic polymer. From the viewpoint of suitably exerting the effect of improving the cohesive force, the amount of the epoxy crosslinking agent to be used is usually suitably about 0.002 parts by weight or more, preferably about 0.005 parts by weight or more, more preferably about 0.01 parts by weight or more, further preferably about 0.02 parts by weight or more, and particularly preferably about 0.03 parts by weight or more, relative to 100 parts by weight of the acrylic polymer. In order to avoid the lowering of initial adhesiveness to an adherend due to excessive crosslinking, the amount of the epoxy crosslinking agent to be used is usually preferably about 0.2 parts by weight or less, and preferably about 0.1 parts by weight or less, based on 100 parts by weight of the acrylic polymer.

As the isocyanate-based crosslinking agent, polyfunctional isocyanates (compounds having an average of 2 or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate-based crosslinking agent may be used alone in 1 kind or in combination of 2 or more kinds. As a preferable polyfunctional isocyanate, a polyfunctional isocyanate having an average of 3 or more isocyanate groups per molecule can be exemplified. The 3 or more functional isocyanate may be a polymer (e.g., dimer or trimer) of a 2 or 3 or more functional isocyanate, a derivative (e.g., addition reaction product of a polyol and 2 or more molecules of a polyfunctional isocyanate), a polymer, or the like. Examples thereof include: a dimer or trimer of diphenylmethane diisocyanate, an isocyanurate body of hexamethylene diisocyanate (a trimer adduct of an isocyanurate structure), a reaction product of trimethylolpropane and tolylene diisocyanate, a reaction product of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and other polyfunctional isocyanates. Examples of commercially available products include: the trade name "DURANATE TPA-100" manufactured by Asahi Kasei Kabushiki Kaisha, the trade name "CORONATE L", "CORONATE HL", "CORONATE HK", "CORONATE HX", "CORONATE 2096" manufactured by Tosoh Kabushiki Kaisha, and the like.

In the embodiment using the isocyanate-based crosslinking agent, the amount thereof is not particularly limited. The amount of the isocyanate-based crosslinking agent to be used may be, for example, about 0.5 part by weight or more and about 10 parts by weight or less based on 100 parts by weight of the acrylic polymer. From the viewpoint of aggregation, the amount of the isocyanate-based crosslinking agent used is usually suitably about 1 part by weight or more, and preferably about 1.5 parts by weight or more, based on 100 parts by weight of the acrylic polymer. The amount of the isocyanate-based crosslinking agent to be used is usually about 8 parts by weight or less, preferably about 5 parts by weight or less (for example, about less than 4 parts by weight) based on 100 parts by weight of the acrylic polymer.

The technique disclosed herein can be preferably carried out using at least an epoxy-based crosslinking agent as the crosslinking agent. In a preferred embodiment, the adhesive composition contains an epoxy-based crosslinking agent as a crosslinking agent and does not substantially contain an isocyanate-based crosslinking agent. As the crosslinking agent, only an epoxy crosslinking agent may be used.

The content of the crosslinking agent (total amount of the crosslinking agent) in the adhesive composition disclosed herein is not particularly limited. From the viewpoint of aggregation, the content of the crosslinking agent is usually about 0.001 parts by weight or more, preferably about 0.002 parts by weight or more, preferably about 0.005 parts by weight or more, more preferably about 0.01 parts by weight or more, further preferably about 0.02 parts by weight or more, and particularly preferably about 0.03 parts by weight or more, based on 100 parts by weight of the acrylic polymer. From the viewpoint of initial adhesiveness to an adherend, the content of the crosslinking agent in the pressure-sensitive adhesive composition is usually about 20 parts by weight or less, preferably about 15 parts by weight or less, and preferably about 10 parts by weight or less (for example, about 5 parts by weight or less), based on 100 parts by weight of the acrylic polymer.

(tackifying resin)

In a preferred embodiment, the adhesive composition (and further the adhesive layer) contains a tackifier resin. As the tackifier resin that can be contained in the adhesive composition, 1 or 2 or more kinds selected from known various tackifier resins such as a phenol-based tackifier resin, a terpene-based tackifier resin, a modified terpene-based tackifier resin, a rosin-based tackifier resin, a hydrocarbon-based tackifier resin, an epoxy-based tackifier resin, a polyamide-based tackifier resin, an elastic-based tackifier resin, and a ketone-based tackifier resin can be used. By using a tackifier resin, the adhesive strength including the initial adhesive strength to an adherend is improved.

Examples of the phenolic tackifying resins include terpene phenol resins, hydrogenated terpene phenol resins, alkyl phenol resins, and rosin phenol resins.

The terpene-phenol resin is a polymer containing a terpene residue and a phenol residue, and is a concept including both a copolymer of a terpene and a phenol compound (terpene-phenol copolymer resin) and a resin obtained by phenol-modifying a terpene or a homopolymer or a copolymer thereof (phenol-modified terpene resin). Suitable examples of terpenes constituting such a terpene-phenol resin include: monoterpenes such as α -pinene, β -pinene, limonene (including d-isomer, l-isomer, and d/l-isomer (dipentene)). The hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. Sometimes also referred to as hydrogenated terpene phenol resins.

The alkylphenol resin is a resin (oleo-phenolic resin) obtained from alkylphenol and formaldehyde. Examples of the alkylphenol resin include a novolak type and a resol type.

The rosin phenol resin is typically a rosin or a phenol-modified product of the above rosin derivatives (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters). Examples of the rosin phenol resin include rosin phenol resins obtained by a method of adding phenol to a rosin or the various rosin derivatives described above with an acid catalyst and performing thermal polymerization.

Among these phenolic tackifying resins, terpene phenol resins, hydrogenated terpene phenol resins, and alkylphenol resins are preferable, terpene phenol resins and hydrogenated terpene phenol resins are more preferable, and terpene phenol resins are particularly preferable.

Examples of the terpene-based tackifier resin include polymers of terpenes (for example, monoterpenes) such as α -pinene, β -pinene, d-limonene, l-limonene, and dipentene. The terpene may be a homopolymer of 1 kind of terpene, or a copolymer of 2 or more kinds of terpenes. Examples of the homopolymer of 1 terpene include an α -pinene polymer, a β -pinene polymer, and a dipentene polymer.

Examples of the modified terpene resin include those obtained by modifying the above terpene resins. Specifically, a styrene-modified terpene resin, a hydrogenated terpene resin, and the like can be exemplified.

The rosin-based tackifier resin referred to herein includes both rosin-based resins and rosin derivative resins. Examples of rosins include: unmodified rosins (raw rosins) such as gum rosin, wood rosin, tall oil rosin and the like: modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, other chemically modified rosins, etc.) obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc.

Rosin derivative resins are typically derivatives of such rosins as described above. The rosin-based resin referred to herein includes a derivative of an unmodified rosin and a derivative of a modified rosin (including hydrogenated rosin, disproportionated rosin and polymerized rosin). Examples thereof include: rosin esters such as an unmodified rosin ester as an ester of an unmodified rosin and an alcohol, and a modified rosin ester as an ester of a modified rosin and an alcohol; for example, unsaturated fatty acid-modified rosins obtained by modifying rosins with unsaturated fatty acids; for example, unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; for example, rosin alcohols obtained by reducing carboxyl groups of rosins or the various rosin derivatives described above (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters); for example, metal salts of rosins or various rosin derivatives described above; and the like. Specific examples of rosin esters include: methyl esters, triethylene glycol esters, glycerol esters, pentaerythritol esters, and the like of unmodified rosins or modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, and the like).

Examples of the hydrocarbon-based tackifier resin include: various hydrocarbon-based resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic/aromatic petroleum resins (styrene/olefin copolymers, etc.), aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, and coumarone/indene-based resins.

The softening point of the tackifier resin is not particularly limited. From the viewpoint of improving cohesive force, a tackifier resin having a softening point (softening temperature) of about 80 ℃ or higher (preferably about 100 ℃ or higher) can be preferably used. For example, a phenolic tackifying resin (terpene phenol resin or the like) having such a softening point can be preferably used. In a preferred embodiment, a terpene-phenol resin having a softening point of about 135 ℃ or higher (further about 140 ℃ or higher) can be used. The upper limit of the softening point of the tackifier resin is not particularly limited. From the viewpoint of adhesion to an adherend or a base film, a tackifier resin having a softening point of about 200 ℃ or less (more preferably about 180 ℃ or less) can be preferably used. The softening point of the tackifier resin can be measured by a softening point test method (ring and ball method) specified in JIS K2207.

A preferable embodiment includes an embodiment in which the tackifier resin contains 1 or 2 or more kinds of phenol-based tackifier resins (for example, terpene-phenol resins). The techniques disclosed herein may be preferably implemented in such a manner that about 25 wt% or more (more preferably about 30 wt% or more) of the total amount of the tackifier resin is a terpene-phenol resin, for example. About 50 wt% or more of the total amount of the tackifier resin may be the terpene-phenol resin, or about 80 wt% or more (for example, about 90 wt% or more) may be the terpene-phenol resin. Substantially all (for example, about 95 wt% or more and 100 wt% or less, and further about 99 wt% or more and 100 wt% or less) of the tackifier resin may be the terpene-phenol resin.

In the embodiment using a tackifier resin, the content of the tackifier resin is not particularly limited, and can be selected according to the purpose and the use mode of the pressure-sensitive adhesive sheet. The content of the tackifier resin may be about 5 parts by weight or more and about 8 parts by weight or more (for example, about 10 parts by weight or more) with respect to 100 parts by weight of the acrylic polymer. The technique disclosed herein can also be preferably carried out in such a manner that the content of the tackifier resin is about 15 parts by weight or more relative to 100 parts by weight of the acrylic polymer. The upper limit of the content of the tackifier resin is not particularly limited. From the viewpoint of compatibility with the acrylic polymer and deformation resistance, the content of the tackifier resin is suitably about 70 parts by weight or less, preferably about 55 parts by weight or less, and more preferably about 45 parts by weight or less (for example, about 40 parts by weight or less, and typically about 30 parts by weight or less) with respect to 100 parts by weight of the acrylic polymer.

(other additives)

The pressure-sensitive adhesive composition may contain, in addition to the above-mentioned components, various additives generally used in the field of pressure-sensitive adhesives, such as a leveling agent, a crosslinking aid, a plasticizer, a softening agent, an antistatic agent, an anti-aging agent, an ultraviolet absorber, an antioxidant, and a light stabilizer, as required. Since conventionally known substances can be used for such various additives by a conventional method, and are not characteristic of the present invention, detailed description thereof will be omitted.

The adhesive layer disclosed herein may be an adhesive layer formed from a water-based adhesive composition, a solvent-based adhesive composition, a hot-melt adhesive composition, or an active energy ray-curable adhesive composition. The aqueous pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition in a form containing a pressure-sensitive adhesive (pressure-sensitive adhesive layer-forming component) in a solvent (aqueous solvent) mainly containing water, and typically includes a pressure-sensitive adhesive composition called an aqueous dispersion type pressure-sensitive adhesive composition (a composition in which at least a part of the pressure-sensitive adhesive is dispersed in water) and the like. The solvent-based adhesive composition is an adhesive composition in which an adhesive is contained in an organic solvent. The technique disclosed herein can be carried out particularly preferably in a mode having an adhesive layer formed from a solvent-based adhesive composition from the viewpoint of adhesive properties and the like.

The adhesive sheet disclosed herein can be formed by a conventionally known method. For example, as a method for forming a substrate-less pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer, a method (direct method) may be employed in which a pressure-sensitive adhesive composition is directly applied (typically, applied) to either one of a first release film and a second release film, and the pressure-sensitive adhesive layer is formed on the release film by drying or curing the composition. Further, a method (transfer method) may be employed in which a pressure-sensitive adhesive layer is formed on a release surface different from the first and second release films by applying a pressure-sensitive adhesive composition to the release surface and drying or curing the pressure-sensitive adhesive composition, and the pressure-sensitive adhesive layer is transferred to either the first release film or the second release film. In both the direct method and the transfer method, a release film-attached pressure-sensitive adhesive sheet is formed by covering the exposed surface of the pressure-sensitive adhesive layer with another release film. When the pressure-sensitive adhesive sheet is formed by a direct method, it is preferable to apply the pressure-sensitive adhesive composition to a second release film having a higher tensile modulus and good handling properties. The pressure-sensitive adhesive layer is typically formed continuously, but is not limited to this form, and may be formed in a regular or irregular pattern such as dots or stripes, for example.

The application of the adhesive composition can be performed using a conventionally known coater such as a gravure coater, die coater, or bar coater. Alternatively, the adhesive composition may be applied by impregnation, curtain coating, or the like.

From the viewpoints of accelerating the crosslinking reaction, improving the production efficiency, and the like, the drying of the binder composition is preferably performed under heating. The drying temperature may be, for example, about 40 to 150 ℃, and is preferably about 60 to 130 ℃. After drying the pressure-sensitive adhesive composition, curing may be further performed for the purpose of adjusting the transfer of components in the pressure-sensitive adhesive layer, advancing the crosslinking reaction, relaxing strain which may be present in the substrate film or the pressure-sensitive adhesive layer, and the like.

The thickness of the adhesive layer is not particularly limited. The thickness of the adhesive layer is usually suitably about 300 μm or less, preferably about 200 μm or less, more preferably about 150 μm or less, and further preferably about 100 μm or less. In a preferred embodiment of the pressure-sensitive adhesive sheet, the thickness of the pressure-sensitive adhesive layer is about 50 μm or less (usually 40 μm or less). The lower limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, but from the viewpoint of adhesiveness and adherend-following property, it is favorably about 3 μm or more, preferably about 6 μm or more, and more preferably about 10 μm or more (for example, about 15 μm or more). The psa sheet with a release film disclosed herein can be suitably implemented, for example, in such a manner that the psa sheet includes a psa layer having a thickness of about 10 μm or more and about 150 μm or less (preferably about 15 μm or more and about 50 μm or less, for example, 20 μm or more and 50 μm or less). A preferable example is a pressure-sensitive adhesive sheet with a release film, which is a non-substrate pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer having the above thickness.

The pressure-sensitive adhesive sheet with a release film disclosed herein can be suitably implemented such that the storage modulus G' (25 ℃) at 25 ℃ of the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet is 0.6MPa or less. From the viewpoint of improving initial adhesiveness to an adherend, it is advantageous that the storage modulus G' of the pressure-sensitive adhesive layer is low, but unintended separation of the pressure-sensitive adhesive sheet tends to easily occur. Therefore, it is of great interest to apply the techniques disclosed herein to inhibit unintended separations. The above G' (25 ℃ C.) may be, for example, 0.4MPa or less, 0.3MPa or less, 0.25MPa or less, or 0.23MPa or less in some cases. The lower limit of the above G' (25 ℃ C.) is not particularly limited, but is usually preferably 0.12MPa or more from the viewpoint of easily exerting a cohesive force suitable for fixation of a member. In some embodiments, the G' (25 ℃ C.) may be 0.15MPa or more, or may be 0.17MPa or more.

The storage modulus G' (25 ℃ C.) of the pressure-sensitive adhesive layer can be determined by dynamic viscoelasticity measurement. Specifically, a plurality of pressure-sensitive adhesive layers (pressure-sensitive adhesive sheets in the case of a non-substrate pressure-sensitive adhesive sheet) to be measured were stacked to prepare a pressure-sensitive adhesive layer having a thickness of about 2 mm. The adhesive layer was fixed to a disk-shaped test piece with a diameter of 7.9mm by sandwiching the test piece between parallel plates, and dynamic viscoelasticity was measured under the following conditions using a viscoelasticity tester (for example, ARES manufactured by TA Instruments, Inc. or its equivalent) to determine the storage modulus G' (25 ℃).

Measurement mode: shear mode

Temperature range: -70 ℃ to 150 DEG C

Temperature increase rate: 5 deg.C/min

Measurement frequency: 1Hz

The measurement was also performed by the above-described method in examples described later.

< substrate >

In the embodiment where the pressure-sensitive adhesive sheet disclosed herein is in the form of a single-sided pressure-sensitive adhesive or double-sided pressure-sensitive adhesive base-attached pressure-sensitive adhesive sheet, a resin film, a foamed film, paper, cloth, a metal foil, a composite thereof, or the like can be used as a base for supporting (backing) the pressure-sensitive adhesive layer. Examples of the resin film include: polyolefin films such as Polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers; polyester films such as polyethylene terephthalate (PET); vinyl chloride resin films; a vinyl acetate resin film; a polyimide resin film; a polyamide resin film; a fluororesin film; cellophane, and the like. Examples of paper include: japanese paper, kraft paper, glassine paper, fine paper, synthetic paper, surface-coated paper, and the like. Examples of the cloth include: woven or nonwoven fabrics obtained from various fibrous materials by themselves or by blending, and the like. Examples of the fibrous material include: cotton, staple fibers, manila hemp, pulp (pulp), rayon, acetate fibers, polyester fibers, polyvinyl alcohol fibers, polyamide fibers, polyolefin fibers, and the like. Examples of the rubber sheet include: natural rubber sheets, butyl rubber sheets, and the like. Examples of the foam sheet include: foamed polyurethane sheets, foamed neoprene sheets, and the like. Examples of the metal foil include: aluminum foil, copper foil, and the like.

The nonwoven fabric used herein mainly refers to a nonwoven fabric for psa sheets used in the field of psa tapes and psa sheets, and typically refers to a nonwoven fabric produced using a general paper machine (which may be referred to as "paper"). The resin film is typically a non-porous resin sheet, and is a concept different from, for example, a nonwoven fabric (i.e., a concept not including a nonwoven fabric). The resin film may be any of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film. The surface of the substrate on which the pressure-sensitive adhesive layer is provided may be subjected to surface treatment such as coating with a primer, corona discharge treatment, or plasma treatment.

The thickness of the base film disclosed herein is not particularly limited. From the viewpoint of avoiding excessive thickening of the adhesive sheet, the thickness of the base film (e.g., resin film) may be, for example, about 200 μm or less, preferably about 150 μm or less, and more preferably about 100 μm or less. The thickness of the base film may be about 70 μm or less, about 50 μm or less, or about 30 μm or less (for example, about 25 μm or less) depending on the purpose and the mode of use of the pressure-sensitive adhesive sheet. In one embodiment, the thickness of the base film may be about 20 μm or less, about 15 μm or less, or about 10 μm or less (e.g., about 5 μm or less). By reducing the thickness of the base film, the thickness of the adhesive layer can be further increased even if the total thickness of the adhesive sheet is the same. This is advantageous from the viewpoint of improving adhesion to the base material. The lower limit of the thickness of the base film is not particularly limited. From the viewpoint of handling (workability), processability, and the like of the psa sheet, the thickness of the substrate film is generally about 0.5 μm or more (e.g., 1 μm or more), preferably about 2 μm or more, e.g., about 4 μm or more. In one embodiment, the thickness of the base film may be about 6 μm or more, about 8 μm or more, or about 10 μm or more (e.g., more than 10 μm).

< use >

The pressure-sensitive adhesive sheet contained in the pressure-sensitive adhesive sheet with a release film disclosed herein is suitable for high smoothness because both the first pressure-sensitive adhesive surface and the second pressure-sensitive adhesive surface are protected by the release film, and can rapidly form a good adhesion state to an adherend. Such a pressure-sensitive adhesive sheet easily exhibits good performance even in a small area, and has excellent initial adhesion to an adherend. The release film-equipped pressure-sensitive adhesive sheet disclosed herein has good unintended separation prevention properties of the pressure-sensitive adhesive sheet when the first release film is removed, and good transferability when the pressure-sensitive adhesive sheet is transferred to an adherend. By utilizing such characteristics, the pressure-sensitive adhesive sheet with a release film can be used in various applications in which initial adhesiveness to an adherend and high transferability are desired. For example, the pressure-sensitive adhesive sheet can be suitably used for applications in which various members are fixed by pressure contact in a short time, or applications in which the pressure-sensitive adhesive sheet is processed into a complicated or precise shape by a multi-stage process including transfer to a process liner and then the pressure-sensitive adhesive sheet is attached to a final adherend. As a typical example, there is a member fixing application of various electronic devices in which a tact time is strictly controlled for mass production and a shape of an adhesive sheet tends to become complicated with miniaturization, a large screen size, improvement of design, and the like. For example, the pressure-sensitive adhesive sheet with a release film disclosed herein can be preferably applied to applications of fixing members in various portable devices (portable apparatuses). Non-limiting examples of the portable electronic device include a mobile phone, a smart phone, a tablet personal computer, a notebook personal computer, various wearable devices (e.g., a wrist-worn type worn on a wrist such as a watch, a modular type worn on a part of a body by a clip, a band, or the like, an eye-worn (eyewear) type including a glasses type (a single-eye type or a double-eye type, also including a helmet type), a clothing type attached to a shirt, a sock, a hat, or the like in the form of a decoration, an ear-worn type attached to an ear such as an earphone, or the like), a digital camera, a digital video camera, an audio device (a portable music player, a recording pen, or the like), a calculator (a desktop calculator, or the like), a portable game device, an electronic dictionary, an electronic organizer, an electronic book, an in-car-mounted information device, a portable radio, a portable television, a portable printer, a portable electronic book, a portable information device, a portable information terminal, and a portable information terminal, Portable scanners, portable modems, and the like. In the present specification, "portable" is not sufficient if it is interpreted as being merely portable, and means having a level of portability at which an individual (a standard adult) can be relatively easily carried.

Matters disclosed in the specification include the following.

(1) A release film-equipped adhesive sheet comprising:

double-sided adhesive pressure-sensitive adhesive sheet,

A first release film disposed on the first adhesive surface of the adhesive sheet, and

a second release film disposed on the second adhesive surface of the adhesive sheet,

tensile modulus E of the second release film ₂ Tensile modulus E relative to the first release film ₁ Ratio of (E) ₂ /E ₁ ) Is 1.5 or more (for example, 1.5 or more and 50 or less).

(2) The pressure-sensitive adhesive sheet with a release film according to the item (1). Wherein the peeling force R from the second peeling film is ₂ Subtracting the peeling force R of the first peeling film ₁ And the difference in peel force (R) defined in the form of the value obtained ₂ -R ₁ ) Is 0.2N/50mm or less (for example, 0.01N/50mm or more and 0.2N/50mm or less).

(3) The pressure-sensitive adhesive sheet with a release film according to the above (1) or (2), wherein the first release film has a maximum test force F in a tensile test ₁ Is 5N or more (for example, 5N or more and 120N or less).

(4) The release film-equipped adhesive sheet according to any one of the above (1) to (3), wherein the second release film has a maximum test force F in a tensile test ₂ Is 30N or more (for example, 30N or more and 200N or less).

(5) The release film-equipped adhesive sheet according to any one of the items (1) to (4), wherein the first release film is a release polyolefin film.

(6) The release film-equipped adhesive sheet according to any one of the items (1) to (5), wherein the second release film is a releasable polyester film.

(7) The pressure-sensitive adhesive sheet with a release film according to any one of the above (1) to (5), wherein the first release film is a release polyethylene film,

the second release film is selected from the group consisting of a release polypropylene film and a release polyester film.

(8) The release film-equipped adhesive sheet according to any one of the above (1) to (7), wherein either one or both of the first release film and the second release film is colored.

(9) The pressure-sensitive adhesive sheet with a release film according to any one of the above (1) to (8), wherein the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet has a storage modulus G' (25 ℃) of 0.60MPa or less (for example, 0.15MPa or more and 0.60MPa or less), or 0.40MPa or less, or 0.30MPa or less at 25 ℃.

(10) The release film-equipped adhesive sheet according to any one of the above (1) to (9), wherein the adhesive sheet is a substrate-free adhesive sheet comprising an adhesive layer.

(11) The release film-equipped adhesive sheet according to any one of the above (1) to (10), wherein the adhesive sheet comprises an acrylic adhesive layer.

(12) The release film-equipped adhesive sheet according to any one of the above (1) to (11), wherein the peel force R of the second release film ₂ Is 0.4N/50mm or less (for example, 0.01N/50mm or more and 0.4N/50mm or less).

(13) The release-film-equipped adhesive sheet according to any one of the above (1) to (12), wherein the peel force R of the first release film ₁ Is 0.3N/50mm or less (for example, 0.01N/50mm or more and 0.3N/50mm or less).

(14) The release film-attached pressure-sensitive adhesive sheet according to any one of (1) to (13) above, wherein the thickness t1 of the first release film is 20 μm or more (for example, 20 μm or more and 150 μm or less).

(15) The release film-attached pressure-sensitive adhesive sheet according to any one of the above (1) to (14), wherein the thickness t of the first release film of the pressure-sensitive adhesive layer ₁ Relative to the thickness t of the second release film ₂ The ratio of (A) is more than 1 and 5 or less.

(16) The release film-equipped adhesive sheet according to any one of the above (1) to (15), wherein the thickness of the adhesive layer is 20 μm or more (for example, 20 μm or more and 200 μm or less).

(17) The release film-equipped adhesive sheet according to any one of (1) to (16) above, which is used for fixing a member in a portable electronic device.

(18) The release film-equipped pressure-sensitive adhesive sheet according to any one of the above (1) to (17), which is used for affixing a member by attaching the first pressure-sensitive adhesive surface to the member.

(19) The release film-equipped pressure-sensitive adhesive sheet according to any one of the above (1) to (18), which is used in a form in which the first pressure-sensitive adhesive surface is stuck to a releasable surface and transferred to the releasable surface.

[ examples ]

The following describes several embodiments related to the present invention, but the present invention is not intended to be limited to these embodiments. In the following description, "part" and "%" are based on weight unless otherwise specified.

< preparation of adhesive composition >

(adhesive composition A)

In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser, and a dropping funnel, 90 parts of 2EHA and 10 parts of AA as monomer components were charged, and further, the mixture was stirred at a rate of about 1: ethyl acetate and toluene as polymerization solvents were added at a ratio of 1 (by volume) and stirred for 2 hours while introducing nitrogen. After the oxygen in the polymerization system was removed in this way, 0.2 part of BPO as a polymerization initiator was added to carry out solution polymerization at 60 ℃ for 6 hours, thereby obtaining a solution of an acrylic polymer a. The Mw of the acrylic polymer A was 94.6 ten thousand. To this solution, 0.05 part of an epoxy-based crosslinking agent (trade name "TETRAD-C", 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, manufactured by Mitsubishi gas chemical Co., Ltd.) and 20 parts of a terpene phenol resin (trade name "Tamanol 803L", manufactured by Mitsubishi chemical industries, Ltd., softening point of about 145 to 160 ℃ C.) were added and mixed with stirring, to 100 parts of the acrylic polymer A contained in the solution, to prepare an adhesive composition A.

(adhesive composition B)

An acrylic polymer B solution was obtained to prepare an adhesive composition B in substantially the same manner as in the preparation of the adhesive composition a except that the composition of the monomer components was changed to 95 parts of BA and 5 parts of AA. The Mw of the acrylic polymer B was 68 ten thousand.

< preparation of pressure-sensitive adhesive sheet with Release film >

(Release film)

A total of 6 kinds of release films (PE #50, PE #80) were prepared, each having a release treatment layer based on a silicone-based release agent on one side of an LDPE film, a release film (OPP #80) having a release treatment layer based on a silicone-based release agent on one side of an OPP film, and 3 kinds of release films (PET #25, PET #38, PET #75) having a release treatment layer based on a silicone-based release agent on one side of a PET film. The composition and properties of each release film are shown in table 1.

[ Table 1]

TABLE 1

(example 1)

The pressure-sensitive adhesive composition A was applied to the release surface of PET #38 as a second release film, and dried at 100 ℃ for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of 30 μm. The first release film PE #50 was applied to the exposed pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer so that the release surface faced the pressure-sensitive adhesive layer. In this manner, a release film-equipped adhesive sheet of example 1 was produced in which the first adhesive surface and the second adhesive surface of the base-less adhesive sheet including the adhesive layer were covered with the first release film (PE #50) and the second release film (PET #38), respectively.

(examples 2 to 12)

Release film-attached pressure-sensitive adhesive sheets of examples 2 to 12 were produced in the same manner as in example 1 except that the pressure-sensitive adhesive compositions, the first release film and the second release film shown in tables 2 and 3 were used.

The storage modulus G '(25 ℃ C.) of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition A was 0.18MPa, and the storage modulus G' (25 ℃ C.) of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition B was 0.25 MPa.

< evaluation >

(evaluation of unintended isolation prevention)

The pressure-sensitive adhesive sheet with a release film of each example was cut into a tape shape having a width of 50mm and a length of 150mm using a commercially available double-sided pressure-sensitive adhesive tape to prepare a sample sheet. The back surface of the second release film constituting each sample piece was fixed to a stainless steel plate with a commercially available double-sided adhesive tape under an atmosphere of 23 ℃ and 50% RH to prepare a sample for measurement. The sample was set in a universal tensile testing machine, and the first release film was peeled off at a tensile speed of 300 mm/min and a peel angle of 180 ℃. The state of the pressure-sensitive adhesive sheet at this time was observed, and unintended separation prevention was evaluated in the following 3 stages. The results are shown in tables 2 and 3.

E: no deformation was observed on the adhesive sheet (unintended separation preventing property was excellent).

G: some deformation was observed on the adhesive sheet, but the adhesive sheet did not float from the second release film (unintended separation prevention property was good).

P: a part of the adhesive sheet is peeled off together with the first release film by being twisted off from the remaining part (unintended separation prevention property is lacking).

(transferability)

The transferability of the pressure-sensitive adhesive sheet from the second release film was evaluated on the basis of the manner of use of the pressure-sensitive adhesive sheet transferred to the release surface of the process liner, with respect to the pressure-sensitive adhesive sheets with release films of examples 7, 8, 11, and 12, except for examples 7, 8, 11, and 12, in which unintended separation occurred in the unintended separation prevention evaluation.

Specifically, a release film for evaluation of transferability having a release treatment layer on one surface thereof with a thickness of 75 μm and a release force of 0.5N/50mm based on a silicone-based release agent was prepared. The back surface of the release film was fixed to a stainless steel plate using a commercially available double-sided pressure-sensitive adhesive tape to obtain an adherend. The pressure-sensitive adhesive sheet with a release film of each example was cut into a tape shape having a width of 20mm to prepare a sample sheet. The first release film was peeled from the sample piece in an atmosphere of 23 ℃ and 50% RH to expose the first pressure-sensitive adhesive surface, and the first pressure-sensitive adhesive surface was pressure-bonded to the adherend (i.e., the release surface of the release film for evaluation of transferability) by reciprocating a 2kg roller 1 time. After 5 minutes from the press-bonding, the second release film was peeled off using a universal tensile tester under the conditions of a tensile speed of 300 mm/minute and a peel angle of 180 ℃. The state of the pressure-sensitive adhesive sheet at this time was observed and evaluated in the following 2 stages. The results are shown in tables 2 and 3.

G: the second release film can be peeled off with the entire pressure-sensitive adhesive sheet remaining on the adherend (good transferability).

P: the pressure-sensitive adhesive sheet is peeled off together with the second release film and cannot be transferred to the surface of an adherend. Or a part of the pressure-sensitive adhesive sheet is peeled off together with the second release film by being twisted off from the remaining part. (transfer property failure).

[ Table 2]

TABLE 2

[ Table 3]

TABLE 3

N.m indicates not determined.

As shown in tables 2 and 3, the elastic modulus ratio (E) ₂ /E ₁ ) Peeling film-attached pressure-sensitive adhesive sheets of examples 1 to 6 having peeling strength (R) of more than 1.5 ₂ -R ₁ ) 0.2N/50mm or less, and also exhibits good unintended separation preventing properties. In addition, when these release film-attached pressure-sensitive adhesive sheets are used, the pressure-sensitive adhesive sheet on the second release film can be transferred to the releasable surface well after the first release film is removed.

On the other hand, the pressure-sensitive adhesive sheets with release films of examples 7 to 12 exhibited poor peeling force (R) ₂ -R ₁ ) When the content is 0.2N/50mm or less, the unintended separation preventing property is insufficient, and the peeling force difference (R) is increased ₂ -R ₁ ) Examples 9 and 10 lack transferability from the second release film to the releasable surface.

Specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The techniques described in the claims include modifications and variations of the specific examples described above.

Claims

1. An adhesive sheet with a release film comprising:

double-sided adhesive sheet,

the first release film disposed on the first adhesive surface of the adhesive sheet, and

The thickness of the first peeling film is 20-250 μm, the peeling force R1 of the _first peeling film is 0.1 N/50mm or more,

The thickness of the second release film is 10-150 μm, and the release force of the second release film is 0.3 N/50mm or less,

The peeling force difference R2 _- R1 defined as _a value obtained by subtracting the peeling force R1 of the _first peeling film from the peeling force R2 of the _second peeling film is 0.2 N/50mm or less,

The ratio E ₂ /E ₁ of the tensile modulus E ₂ of the second release film to the tensile modulus E ₁ of the first release film is 1.5 or more,

The pressure-sensitive adhesive sheet is a base-free pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer,

The first release film is a release polyolefin film, and the second release film is a release polyester film.

2 . The pressure-sensitive adhesive sheet with a release film according to claim 1 , wherein the maximum test force F ₁ of the first release film in a tensile test is 5 N or more. 3 .

3 . The pressure-sensitive adhesive sheet with a release film according to claim 1 , wherein the maximum test force F ₂ of the second release film in a tensile test is 30 N or more. 4 .

The pressure-sensitive adhesive sheet with a release film according to claim 1, wherein the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet has a storage modulus G' (25°C) at 25°C of 0.6 MPa or less.

5 . The release film-attached pressure-sensitive adhesive sheet according to claim 1 , which is used for fixing a member in a portable electronic device. 6 .